TY - BOOK A1 - Schmiedgen, Jan A1 - Rhinow, Holger A1 - Köppen, Eva A1 - Meinel, Christoph T1 - Parts without a whole? BT - The current state of Design Thinking practice in organizations N2 - This explorative study gives a descriptive overview of what organizations do and experience when they say they practice design thinking. It looks at how the concept has been appropriated in organizations and also describes patterns of design thinking adoption. The authors use a mixed-method research design fed by two sources: questionnaire data and semi-structured personal expert interviews. The study proceeds in six parts: (1) design thinking¹s entry points into organizations; (2) understandings of the descriptor; (3) its fields of application and organizational localization; (4) its perceived impact; (5) reasons for its discontinuation or failure; and (6) attempts to measure its success. In conclusion the report challenges managers to be more conscious of their current design thinking practice. The authors suggest a co-evolution of the concept¹s introduction with innovation capability building and the respective changes in leadership approaches. It is argued that this might help in unfolding design thinking¹s hidden potentials as well as preventing unintended side-effects such as discontented teams or the dwindling authority of managers. N2 - Diese explorative Studie gibt einen deskriptiven Überblick, was Organisationen tun und zu erleben, wenn sie sagen, sie üben Design Thinking. Es untersucht, wie das Konzept in Organisationen angeeignet und beschreibt auch Muster der Design Thinking Annahme. Die Autoren verwenden eine von zwei Quellen gespeist Mixed-Verfahren Forschungsdesign: Fragebogendaten und semi-strukturierten persönlichen Experteninterviews. Die Studie läuft in sechs Teile: Einstiegspunkte (1) Design-Denken in Organisationen; (2) Verständnis des Deskriptors; (3) ihre Anwendungsgebiete und organisatorische Lokalisierung;(4) dessen empfundenen Auswirkungen; (5) Gründe für ihre Einstellung oder Misserfolg; und (6) versucht, den Erfolg zu messen. Abschließend fordert der Bericht-Manager mehr bewusst ihre aktuellen Design Thinking der Praxis zu sein. Die Autoren schlagen eine Ko-Evolution von Einführung des Konzepts mit Innovationsfähigkeit Gebäude und den jeweiligen Führungswechsel Ansätze. Es wird argumentiert, dass dies in der Entfaltung versteckte Potentiale Design Denken wie auch zur Verhinderung unbeabsichtigten Nebenwirkungen, wie unzufrieden Teams oder die schwindende Autorität von Managern zu helfen. T3 - Technische Berichte des Hasso-Plattner-Instituts für Digital Engineering an der Universität Potsdam - 97 KW - design thinking KW - innovation KW - innovation management KW - innovation capabilities KW - organizational change KW - change management KW - management KW - adoption KW - diffusion KW - study KW - leadership KW - Design Thinking KW - Innovation KW - Innovationsmanagement KW - Organisationsveränderung KW - Change Management KW - Management KW - Innovationsmethode KW - Studie KW - Leadership Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-79969 SN - 978-3-86956-334-3 SN - 1613-5652 SN - 2191-1665 IS - 97 PB - Universitätsverlag Potsdam CY - Potsdam ER - TY - JOUR A1 - Schneider, Johannes A1 - Wenig, Phillip A1 - Papenbrock, Thorsten T1 - Distributed detection of sequential anomalies in univariate time series JF - The VLDB journal : the international journal on very large data bases N2 - The automated detection of sequential anomalies in time series is an essential task for many applications, such as the monitoring of technical systems, fraud detection in high-frequency trading, or the early detection of disease symptoms. All these applications require the detection to find all sequential anomalies possibly fast on potentially very large time series. In other words, the detection needs to be effective, efficient and scalable w.r.t. the input size. Series2Graph is an effective solution based on graph embeddings that are robust against re-occurring anomalies and can discover sequential anomalies of arbitrary length and works without training data. Yet, Series2Graph is no t scalable due to its single-threaded approach; it cannot, in particular, process arbitrarily large sequences due to the memory constraints of a single machine. In this paper, we propose our distributed anomaly detection system, short DADS, which is an efficient and scalable adaptation of Series2Graph. Based on the actor programming model, DADS distributes the input time sequence, intermediate state and the computation to all processors of a cluster in a way that minimizes communication costs and synchronization barriers. Our evaluation shows that DADS is orders of magnitude faster than S2G, scales almost linearly with the number of processors in the cluster and can process much larger input sequences due to its scale-out property. KW - Distributed programming KW - Sequential anomaly KW - Actor model KW - Data mining KW - Time series Y1 - 2021 U6 - https://doi.org/10.1007/s00778-021-00657-6 SN - 1066-8888 SN - 0949-877X VL - 30 IS - 4 SP - 579 EP - 602 PB - Springer CY - Berlin ER - TY - GEN A1 - Schneider, Oliver A1 - Shigeyama, Jotaro A1 - Kovacs, Robert A1 - Roumen, Thijs Jan A1 - Marwecki, Sebastian A1 - Böckhoff, Nico A1 - Glöckner, Daniel Amadeus Johannes A1 - Bounama, Jonas A1 - Baudisch, Patrick T1 - DualPanto BT - a haptic device that enables blind users to continuously interact with virtual worlds T2 - UIST '18: Proceedings of the 31st Annual ACM Symposium on User Interface Software and Technology N2 - We present a new haptic device that enables blind users to continuously track the absolute position of moving objects in spatial virtual environments, as is the case in sports or shooter games. Users interact with DualPanto by operating the me handle with one hand and by holding on to the it handle with the other hand. Each handle is connected to a pantograph haptic input/output device. The key feature is that the two handles are spatially registered with respect to each other. When guiding their avatar through a virtual world using the me handle, spatial registration enables users to track moving objects by having the device guide the output hand. This allows blind players of a 1-on-1 soccer game to race for the ball or evade an opponent; it allows blind players of a shooter game to aim at an opponent and dodge shots. In our user study, blind participants reported very high enjoyment when using the device to play (6.5/7). KW - Haptics KW - force-feedback KW - accessibility KW - blind KW - visually impaired KW - gaming Y1 - 2018 SN - 978-1-4503-5948-1 U6 - https://doi.org/10.1145/3242587.3242604 SP - 877 EP - 887 PB - Association for Computing Machinery CY - New York ER - TY - JOUR A1 - Schneider, Sven A1 - Lambers, Leen A1 - Orejas, Fernando T1 - Automated reasoning for attributed graph properties JF - International Journal on Software Tools for Technology Transfer N2 - Graphs are ubiquitous in computer science. Moreover, in various application fields, graphs are equipped with attributes to express additional information such as names of entities or weights of relationships. Due to the pervasiveness of attributed graphs, it is highly important to have the means to express properties on attributed graphs to strengthen modeling capabilities and to enable analysis. Firstly, we introduce a new logic of attributed graph properties, where the graph part and attribution part are neatly separated. The graph part is equivalent to first-order logic on graphs as introduced by Courcelle. It employs graph morphisms to allow the specification of complex graph patterns. The attribution part is added to this graph part by reverting to the symbolic approach to graph attribution, where attributes are represented symbolically by variables whose possible values are specified by a set of constraints making use of algebraic specifications. Secondly, we extend our refutationally complete tableau-based reasoning method as well as our symbolic model generation approach for graph properties to attributed graph properties. Due to the new logic mentioned above, neatly separating the graph and attribution parts, and the categorical constructions employed only on a more abstract level, we can leave the graph part of the algorithms seemingly unchanged. For the integration of the attribution part into the algorithms, we use an oracle, allowing for flexible adoption of different available SMT solvers in the actual implementation. Finally, our automated reasoning approach for attributed graph properties is implemented in the tool AutoGraph integrating in particular the SMT solver Z3 for the attribute part of the properties. We motivate and illustrate our work with a particular application scenario on graph database query validation. KW - Attributed graphs KW - Nested graph conditions KW - Model generation KW - Tableau method KW - Graph queries Y1 - 2018 U6 - https://doi.org/10.1007/s10009-018-0496-3 SN - 1433-2779 SN - 1433-2787 VL - 20 IS - 6 SP - 705 EP - 737 PB - Springer CY - Heidelberg ER - TY - JOUR A1 - Schneider, Sven A1 - Lambers, Leen A1 - Orejas, Fernando T1 - A logic-based incremental approach to graph repair featuring delta preservation JF - International journal on software tools for technology transfer : STTT N2 - We introduce a logic-based incremental approach to graph repair, generating a sound and complete (upon termination) overview of least-changing graph repairs from which a user may select a graph repair based on non-formalized further requirements. This incremental approach features delta preservation as it allows to restrict the generation of graph repairs to delta-preserving graph repairs, which do not revert the additions and deletions of the most recent consistency-violating graph update. We specify consistency of graphs using the logic of nested graph conditions, which is equivalent to first-order logic on graphs. Technically, the incremental approach encodes if and how the graph under repair satisfies a graph condition using the novel data structure of satisfaction trees, which are adapted incrementally according to the graph updates applied. In addition to the incremental approach, we also present two state-based graph repair algorithms, which restore consistency of a graph independent of the most recent graph update and which generate additional graph repairs using a global perspective on the graph under repair. We evaluate the developed algorithms using our prototypical implementation in the tool AutoGraph and illustrate our incremental approach using a case study from the graph database domain. KW - Nested graph conditions KW - Graph repair KW - Model repair KW - Consistency KW - restoration KW - Delta preservation KW - Graph databases KW - Model-driven KW - engineering Y1 - 2021 U6 - https://doi.org/10.1007/s10009-020-00584-x SN - 1433-2779 SN - 1433-2787 VL - 23 IS - 3 SP - 369 EP - 410 PB - Springer CY - Berlin ; Heidelberg ER - TY - BOOK A1 - Schneider, Sven A1 - Lambers, Leen A1 - Orejas, Fernando T1 - Symbolic model generation for graph properties N2 - Graphs are ubiquitous in Computer Science. For this reason, in many areas, it is very important to have the means to express and reason about graph properties. In particular, we want to be able to check automatically if a given graph property is satisfiable. Actually, in most application scenarios it is desirable to be able to explore graphs satisfying the graph property if they exist or even to get a complete and compact overview of the graphs satisfying the graph property. We show that the tableau-based reasoning method for graph properties as introduced by Lambers and Orejas paves the way for a symbolic model generation algorithm for graph properties. Graph properties are formulated in a dedicated logic making use of graphs and graph morphisms, which is equivalent to firstorder logic on graphs as introduced by Courcelle. Our parallelizable algorithm gradually generates a finite set of so-called symbolic models, where each symbolic model describes a set of finite graphs (i.e., finite models) satisfying the graph property. The set of symbolic models jointly describes all finite models for the graph property (complete) and does not describe any finite graph violating the graph property (sound). Moreover, no symbolic model is already covered by another one (compact). Finally, the algorithm is able to generate from each symbolic model a minimal finite model immediately and allows for an exploration of further finite models. The algorithm is implemented in the new tool AutoGraph. N2 - Graphen sind allgegenwärtig in der Informatik. Daher ist die Verfügbarkeit von Methoden zur Darstellung und Untersuchung von Grapheigenschaften in vielen Gebieten von großer Wichtigkeit. Insbesondere ist die vollautomatische Überprüfung von Grapheigenschaften auf Erfüllbarkeit von zentraler Bedeutung. Darüberhinaus ist es in vielen Anwendungsszenarien wünschenswert diejenigen Graphen geeignet aufzuzählen, die eine Grapheigenschaft erfüllen. Im Falle einer unendlich großen Anzahl von solchen Graphen ist ein kompletter und gleichzeitig kompakter Überblick über diese Graphen anzustreben. Wir zeigen, dass die Tableau-Methode für Grapheigenschaften von Lambers und Orejas den Weg für einen Algorithmus zur Generierung von symbolischen Modellen frei gemacht hat. Wir formulieren Grapheigenschaften hierbei in einer dedizierten Logik basierend auf Graphen und Graphmorphismen. Diese Logik ist äquivalent zu der First-Order Logic auf Graphen, wie sie von Courcelle eingeführt wurde. Unser parallelisierbarer Algorithmus bestimmt graduell eine endliche Menge von sogenannten symbolischen Modellen. Hierbei beschreibt jedes symbolische Modell eine Menge von endlichen Graphen, die die Grapheigenschaft erfüllen. Die symbolischen Modelle decken so gemeinsam alle endlichen Modelle ab, die die Grapheigenschaft erfüllen (Vollständigkeit) und beschreiben keine endlichen Graphen, die die Grapheigenschaft verletzen (Korrektheit). Außerdem wird kein symbolisches Modell von einem anderen abgedeckt (Kompaktheit). Letztlich ist der Algorithmus in der Lage aus jedem symbolischen Modell ein minimales endliches Modell zu extrahieren und weitere endliche Modelle abzuleiten. Der Algorithmus ist in dem neuen Werkzeug AutoGraph implementiert. T3 - Technische Berichte des Hasso-Plattner-Instituts für Digital Engineering an der Universität Potsdam - 115 KW - model generation KW - nested graph conditions KW - tableau method KW - graph transformation KW - satisfiabilitiy solving KW - Modellerzeugung KW - verschachtelte Graphbedingungen KW - Tableaumethode KW - Graphtransformation KW - Erfüllbarkeitsanalyse Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-103171 SN - 978-3-86956-396-1 SN - 1613-5652 SN - 2191-1665 IS - 115 PB - Universitätsverlag Potsdam CY - Potsdam ER - TY - BOOK A1 - Schreiber, Robin A1 - Krahn, Robert A1 - Ingalls, Daniel H. H. A1 - Hirschfeld, Robert T1 - Transmorphic T1 - Transmorphic BT - mapping direct manipulation to source code transformations BT - Abbilden von direkter Manipulation zu Transformationen im Programmtext N2 - Defining Graphical User Interfaces (GUIs) through functional abstractions can reduce the complexity that arises from mutable abstractions. Recent examples, such as Facebook's React GUI framework have shown, how modelling the view as a functional projection from the application state to a visual representation can reduce the number of interacting objects and thus help to improve the reliabiliy of the system. This however comes at the price of a more rigid, functional framework where programmers are forced to express visual entities with functional abstractions, detached from the way one intuitively thinks about the physical world. In contrast to that, the GUI Framework Morphic allows interactions in the graphical domain, such as grabbing, dragging or resizing of elements to evolve an application at runtime, providing liveness and directness in the development workflow. Modelling each visual entity through mutable abstractions however makes it difficult to ensure correctness when GUIs start to grow more complex. Furthermore, by evolving morphs at runtime through direct manipulation we diverge more and more from the symbolic description that corresponds to the morph. Given that both of these approaches have their merits and problems, is there a way to combine them in a meaningful way that preserves their respective benefits? As a solution for this problem, we propose to lift Morphic's concept of direct manipulation from the mutation of state to the transformation of source code. In particular, we will explore the design, implementation and integration of a bidirectional mapping between the graphical representation and a functional and declarative symbolic description of a graphical user interface within a self hosted development environment. We will present Transmorphic, a functional take on the Morphic GUI Framework, where the visual and structural properties of morphs are defined in a purely functional, declarative fashion. In Transmorphic, the developer is able to assemble different morphs at runtime through direct manipulation which is automatically translated into changes in the code of the application. In this way, the comprehensiveness and predictability of direct manipulation can be used in the context of a purely functional GUI, while the effects of the manipulation are reflected in a medium that is always in reach for the programmer and can even be used to incorporate the source transformations into the source files of the application. N2 - Das Definieren von graphischen Benutzeroberflächen mittels funktionaler Abstraktionen, kann die Komplexität der Verwaltung des Zustandes der Anwendung erheblich reduzieren. Aktuelle Beispiele, wie Facebook's Framework *React*, zeigen auf, wie das modellieren der visuellen Schnittstelle als eine funktionale Projektion vom Zustand der Anwendung zur graphischen Repräsentation, die Anzahl der agierenden Objekte erheblich reduzieren und so die Verlässlichkeit des Systems erhöhen kann. Der Preis für die so erreichte Stabilität, ist eine relativ statische graphische Repräsentation, die sich zur Laufzeit nicht dynamisch anpassen lässt und in der jede visuelle Entität nur mittles funktionaler Abstraktionen beschrieben werden kann, was nicht unserem intuitiven Verständnis der Welt entspricht. Im Gegensatz dazu, erlaubt das Rahmenwerk Morphic mittles Interaktionen wie Ziehen, Greifen oder Skalieren von visuellen Elementen, die grahische Darstellung der Anwendung zur Laufzeit in einer unmittelbaren ("live") und direkten Art und Weise weiter zu entwickeln. Um diese Flexibilität zu erreichen, modelliert Morphic allerdings jedes graphische Objekt mittels veränderlichem Zustand, was das Garantieren der Fehlerfreiheit von graphischen Oberfläche, insbesondere bei sehr komplexen Schnittstellen, deutlich erschwehrt. Hinzu kommt, dass die dynamischen Anpassungen zur Laufzeit dazu führen, dass sich die Oberfläche mehr und mehr von ihrer ursprünglichen symbolischen Definition entfernt, da Morphic von selbst die Änderungen in der Laufzeit nicht im Quellcode reflektieren kann. Die Frage ist also ob es eine Kombination beider Ansätze gibt, welche es vermag die Vorteile zu erhalten und Nachteile wenn möglich auszugleichen. Als Lösung für dieses Problem schlagen wir vor das Konzept der direkten Manipulation aus Morphic auf Transformationen im Quellcode zu übertragen. Hierfür werden wir das Design, die Implementierung und Integration einer bidirektionalen Abbildung zwischen graphischer Darstellung und einer funktionalen, deklarativen symbolischen Beschreibung in einer selbsterhaltenden Entwicklungsumgebung erörtern. Wir werden Transmorphic vorstellen, eine funktionale Variante des Morphic Frameworks, in der visuelle und strukturelle Eigenschaften in einer strikt funktionalen und daher deklarativen Art und Weise definiert werden. Innerhalb von Transmorphic hat der Entwickler die Möglichkeit verschieden Morphs zur Laufzeit mittels direkter Manipulation zusammenzusetzen, was direkt zu Änderungen im Quellcode der Anwendung übersetzt wird. Auf diese Weise kann die verständliche und nachvollziehbare direkte Interaktion aus Morphic, im Kontext einer vollständig funktional beschriebenen graphischen Benutzeroberfläche verwendet werden. T3 - Technische Berichte des Hasso-Plattner-Instituts für Digital Engineering an der Universität Potsdam - 110 KW - functional programming KW - morphic KW - functional lenses KW - direct manipulation KW - synchronization KW - FRP KW - reactive KW - immutable values KW - live programming KW - funktionale Programmierung KW - Morphic KW - Functional Lenses KW - direkte Manipulation KW - Synchronisation KW - FRP KW - reaktive Programmierung KW - Unveränderlichkeit KW - Live-Programmierung Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-98300 SN - 978-3-86956-387-9 SN - 1613-5652 SN - 2191-1665 IS - 110 PB - Universitätsverlag Potsdam CY - Potsdam ER - TY - BOOK A1 - Schwalb, David A1 - Krüger, Jens A1 - Plattner, Hasso T1 - Cache conscious column organization in in-memory column stores N2 - Cost models are an essential part of database systems, as they are the basis of query performance optimization. Based on predictions made by cost models, the fastest query execution plan can be chosen and executed or algorithms can be tuned and optimised. In-memory databases shifts the focus from disk to main memory accesses and CPU costs, compared to disk based systems where input and output costs dominate the overall costs and other processing costs are often neglected. However, modelling memory accesses is fundamentally different and common models do not apply anymore. This work presents a detailed parameter evaluation for the plan operators scan with equality selection, scan with range selection, positional lookup and insert in in-memory column stores. Based on this evaluation, a cost model based on cache misses for estimating the runtime of the considered plan operators using different data structures is developed. Considered are uncompressed columns, bit compressed and dictionary encoded columns with sorted and unsorted dictionaries. Furthermore, tree indices on the columns and dictionaries are discussed. Finally, partitioned columns consisting of one partition with a sorted and one with an unsorted dictionary are investigated. New values are inserted in the unsorted dictionary partition and moved periodically by a merge process to the sorted partition. An efficient attribute merge algorithm is described, supporting the update performance required to run enterprise applications on read-optimised databases. Further, a memory traffic based cost model for the merge process is provided. N2 - Kostenmodelle sind ein essentieller Teil von Datenbanksystemen und bilden die Basis für Optimierungen von Ausführungsplänen. Durch Abschätzungen der Kosten können die entsprechend schnellsten Operatoren und Algorithmen zur Abarbeitung einer Anfrage ausgewählt und ausgeführt werden. Hauptspeicherresidente Datenbanken verschieben den Fokus von I/O Operationen hin zu Zugriffen auf den Hauptspeicher und CPU Kosten, verglichen zu Datenbanken deren primäre Kopie der Daten auf Sekundärspeicher liegt und deren Kostenmodelle sich in der Regel auf die kostendominierenden Zugriffe auf das Sekundärmedium beschränken. Kostenmodelle für Zugriffe auf Hauptspeicher unterscheiden sich jedoch fundamental von Kostenmodellen für Systeme basierend auf Festplatten, so dass alte Modelle nicht mehr greifen. Diese Arbeit präsentiert eine detaillierte Parameterdiskussion, sowie ein Kostenmodell basierend auf Cache-Zugriffen zum Abschätzen der Laufzeit von Datenbankoperatoren in spaltenorientierten und hauptspeicherresidenten Datenbanken wie das Selektieren von Werten einer Spalte mittels einer Gleichheitsbedingung oder eines Wertebereichs, das Nachschlagen der Werte einzelner Positionen oder dem Hinzufügen neuer Werte. Dabei werden Kostenfunktionen für die Operatoren erstellt, welche auf unkomprimierten Spalten, mittels Substitutionskompression komprimierten Spalten sowie bit-komprimierten Spalten operieren. Des Weiteren werden Baumstrukturen als Index Strukturen auf Spalten und Wörterbüchern in die Betrachtung gezogen. Abschließend werden partitionierte Spalten eingeführt, welche aus einer lese- und einer schreib-optimierten Partition bestehen. Neu Werte werden in die schreiboptimierte Partition eingefügt und periodisch von einem Attribut-Merge-Prozess mit der leseoptimierten Partition zusammengeführt. Beschrieben wird eine Effiziente Implementierung für den Attribut-Merge-Prozess und ein Hauptspeicher-bandbreitenbasiertes Kostenmodell aufgestellt. T3 - Technische Berichte des Hasso-Plattner-Instituts für Digital Engineering an der Universität Potsdam - 67 KW - Hauptspeicherdatenbank KW - Datenbank-Kostenmodell KW - Attribut-Merge-Prozess KW - In-Memory Database KW - Database Cost Model KW - Attribute Merge Process Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-63890 SN - 978-3-86956-228-5 PB - Universitätsverlag Potsdam CY - Potsdam ER - TY - THES A1 - Seibel, Andreas T1 - Traceability and model management with executable and dynamic hierarchical megamodels T1 - Traceability und Modell Management mit ausführbaren und dynamischen Megamodellen N2 - Nowadays, model-driven engineering (MDE) promises to ease software development by decreasing the inherent complexity of classical software development. In order to deliver on this promise, MDE increases the level of abstraction and automation, through a consideration of domain-specific models (DSMs) and model operations (e.g. model transformations or code generations). DSMs conform to domain-specific modeling languages (DSMLs), which increase the level of abstraction, and model operations are first-class entities of software development because they increase the level of automation. Nevertheless, MDE has to deal with at least two new dimensions of complexity, which are basically caused by the increased linguistic and technological heterogeneity. The first dimension of complexity is setting up an MDE environment, an activity comprised of the implementation or selection of DSMLs and model operations. Setting up an MDE environment is both time-consuming and error-prone because of the implementation or adaptation of model operations. The second dimension of complexity is concerned with applying MDE for actual software development. Applying MDE is challenging because a collection of DSMs, which conform to potentially heterogeneous DSMLs, are required to completely specify a complex software system. A single DSML can only be used to describe a specific aspect of a software system at a certain level of abstraction and from a certain perspective. Additionally, DSMs are usually not independent but instead have inherent interdependencies, reflecting (partial) similar aspects of a software system at different levels of abstraction or from different perspectives. A subset of these dependencies are applications of various model operations, which are necessary to keep the degree of automation high. This becomes even worse when addressing the first dimension of complexity. Due to continuous changes, all kinds of dependencies, including the applications of model operations, must also be managed continuously. This comprises maintaining the existence of these dependencies and the appropriate (re-)application of model operations. The contribution of this thesis is an approach that combines traceability and model management to address the aforementioned challenges of configuring and applying MDE for software development. The approach is considered as a traceability approach because it supports capturing and automatically maintaining dependencies between DSMs. The approach is considered as a model management approach because it supports managing the automated (re-)application of heterogeneous model operations. In addition, the approach is considered as a comprehensive model management. Since the decomposition of model operations is encouraged to alleviate the first dimension of complexity, the subsequent composition of model operations is required to counteract their fragmentation. A significant portion of this thesis concerns itself with providing a method for the specification of decoupled yet still highly cohesive complex compositions of heterogeneous model operations. The approach supports two different kinds of compositions - data-flow compositions and context compositions. Data-flow composition is used to define a network of heterogeneous model operations coupled by sharing input and output DSMs alone. Context composition is related to a concept used in declarative model transformation approaches to compose individual model transformation rules (units) at any level of detail. In this thesis, context composition provides the ability to use a collection of dependencies as context for the composition of other dependencies, including model operations. In addition, the actual implementation of model operations, which are going to be composed, do not need to implement any composition concerns. The approach is realized by means of a formalism called an executable and dynamic hierarchical megamodel, based on the original idea of megamodels. This formalism supports specifying compositions of dependencies (traceability and model operations). On top of this formalism, traceability is realized by means of a localization concept, and model management by means of an execution concept. N2 - Die modellgetriebene Softwareentwicklung (MDE) verspricht heutzutage, durch das Verringern der inhärenten Komplexität der klassischen Softwareentwicklung, das Entwickeln von Software zu vereinfachen. Um dies zu erreichen, erhöht MDE das Abstraktions- und Automationsniveau durch die Einbindung domänenspezifischer Modelle (DSMs) und Modelloperationen (z.B. Modelltransformationen oder Codegenerierungen). DSMs sind konform zu domänenspezifischen Modellierungssprachen (DSMLs), die dazu dienen das Abstraktionsniveau der Softwareentwicklung zu erhöhen. Modelloperationen sind essentiell für die Softwareentwicklung da diese den Grad der Automatisierung erhöhen. Dennoch muss MDE mit Komplexitätsdimensionen umgehen die sich grundsätzlich aus der erhöhten sprachlichen und technologischen Heterogenität ergeben. Die erste Komplexitätsdimension ist das Konfigurieren einer Umgebung für MDE. Diese Aktivität setzt sich aus der Implementierung und Selektion von DSMLs sowie Modelloperationen zusammen. Eine solche Aktivität ist gerade durch die Implementierung und Anpassung von Modelloperationen zeitintensiv sowie fehleranfällig. Die zweite Komplexitätsdimension hängt mit der Anwendung von MDE für die eigentliche Softwareentwicklung zusammen. Das Anwenden von MDE ist eine Herausforderung weil eine Menge von heterogenen DSMs, die unterschiedlichen DSMLs unterliegen, erforderlich sind um ein komplexes Softwaresystem zu spezifizieren. Individuelle DSMLs werden verwendet um spezifische Aspekte eines Softwaresystems auf bestimmten Abstraktionsniveaus und aus bestimmten Perspektiven zu beschreiben. Hinzu kommt, dass DSMs sowie DSMLs grundsätzlich nicht unabhängig sind, sondern inhärente Abhängigkeiten besitzen. Diese Abhängigkeiten reflektieren äquivalente Aspekte eines Softwaresystems. Eine Teilmenge dieser Abhängigkeiten reflektieren Anwendungen diverser Modelloperationen, die notwendig sind um den Grad der Automatisierung hoch zu halten. Dies wird erschwert wenn man die erste Komplexitätsdimension hinzuzieht. Aufgrund kontinuierlicher Änderungen der DSMs, müssen alle Arten von Abhängigkeiten, inklusive die Anwendung von Modelloperationen, kontinuierlich verwaltet werden. Dies beinhaltet die Wartung dieser Abhängigkeiten und das sachgerechte (wiederholte) Anwenden von Modelloperationen. Der Beitrag dieser Arbeit ist ein Ansatz, der die Bereiche Traceability und Model Management vereint. Das Erfassen und die automatische Verwaltung von Abhängigkeiten zwischen DSMs unterstützt Traceability, während das (automatische) wiederholte Anwenden von heterogenen Modelloperationen Model Management ermöglicht. Dadurch werden die zuvor erwähnten Herausforderungen der Konfiguration und Anwendung von MDE überwunden. Die negativen Auswirkungen der ersten Komplexitätsdimension können gelindert werden indem Modelloperationen in atomare Einheiten zerlegt werden. Um der implizierten Fragmentierung entgegenzuwirken, erfordert dies allerdings eine nachfolgende Komposition der Modelloperationen. Der Ansatz wird als erweitertes Model Management betrachtet, da ein signifikanter Anteil dieser Arbeit die Kompositionen von heterogenen Modelloperationen behandelt. Unterstützt werden zwei unterschiedliche Arten von Kompositionen. Datenfluss-Kompositionen werden verwendet, um Netzwerke von heterogenen Modelloperationen zu beschreiben, die nur durch das Teilen von Ein- und Ausgabe DSMs komponiert werden. Kontext-Kompositionen bedienen sich eines Konzepts, das von deklarativen Modelltransformationen bekannt ist. Dies ermöglicht die Komposition von unabhängigen Transformationsregeln auf unterschiedlichsten Detailebenen. Die in dieser Arbeit eingeführten Kontext-Kompositionen bieten die Möglichkeit eine Menge von unterschiedlichsten Abhängigkeiten als Kontext für eine Komposition zu verwenden -- unabhängig davon ob diese Abhängigkeit eine Modelloperation repräsentiert. Zusätzlich müssen die Modelloperationen, die komponiert werden, selber keine Kompositionsaspekte implementieren, was deren Wiederverwendbarkeit erhöht. Realisiert wird dieser Ansatz durch einen Formalismus der Executable and Dynamic Hierarchical Megamodel genannt wird und auf der originalen Idee der Megamodelle basiert. Auf Basis dieses Formalismus' sind die Konzepte Traceability (hier Localization) und Model Management (hier Execution) umgesetzt. KW - Traceability KW - Modell Management KW - Megamodell KW - Modellgetriebene Entwicklung KW - Komposition KW - Traceability KW - Model Management KW - Megamodel KW - Model-Driven Engineering KW - Composition Y1 - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-64222 ER - TY - JOUR A1 - Seibel, Andreas A1 - Neumann, Stefan A1 - Giese, Holger T1 - Dynamic hierarchical mega models : comprehensive traceability and its efficient maintenance N2 - In the world of model-driven engineering (MDE) support for traceability and maintenance of traceability information is essential. On the one hand, classical traceability approaches for MDE address this need by supporting automated creation of traceability information on the model element level. On the other hand, global model management approaches manually capture traceability information on the model level. However, there is currently no approach that supports comprehensive traceability, comprising traceability information on both levels, and efficient maintenance of traceability information, which requires a high-degree of automation and scalability. In this article, we present a comprehensive traceability approach that combines classical traceability approaches for MDE and global model management in form of dynamic hierarchical mega models. We further integrate efficient maintenance of traceability information based on top of dynamic hierarchical mega models. The proposed approach is further outlined by using an industrial case study and by presenting an implementation of the concepts in form of a prototype. Y1 - 2010 UR - http://www.springerlink.com/content/109378 U6 - https://doi.org/10.1007/s10270-009-0146-z SN - 1619-1366 ER - TY - GEN A1 - Seidel, Felix A1 - Krentz, Konrad-Felix A1 - Meinel, Christoph T1 - Deep En-Route Filtering of Constrained Application Protocol (CoAP) Messages on 6LoWPAN Border Routers T2 - 2019 IEEE 5th World Forum on Internet of Things (WF-IoT) N2 - Devices on the Internet of Things (IoT) are usually battery-powered and have limited resources. Hence, energy-efficient and lightweight protocols were designed for IoT devices, such as the popular Constrained Application Protocol (CoAP). Yet, CoAP itself does not include any defenses against denial-of-sleep attacks, which are attacks that aim at depriving victim devices of entering low-power sleep modes. For example, a denial-of-sleep attack against an IoT device that runs a CoAP server is to send plenty of CoAP messages to it, thereby forcing the IoT device to expend energy for receiving and processing these CoAP messages. All current security solutions for CoAP, namely Datagram Transport Layer Security (DTLS), IPsec, and OSCORE, fail to prevent such attacks. To fill this gap, Seitz et al. proposed a method for filtering out inauthentic and replayed CoAP messages "en-route" on 6LoWPAN border routers. In this paper, we expand on Seitz et al.'s proposal in two ways. First, we revise Seitz et al.'s software architecture so that 6LoWPAN border routers can not only check the authenticity and freshness of CoAP messages, but can also perform a wide range of further checks. Second, we propose a couple of such further checks, which, as compared to Seitz et al.'s original checks, more reliably protect IoT devices that run CoAP servers from remote denial-of-sleep attacks, as well as from remote exploits. We prototyped our solution and successfully tested its compatibility with Contiki-NG's CoAP implementation. Y1 - 2019 SN - 978-1-5386-4980-0 SN - 978-1-5386-4981-7 U6 - https://doi.org/10.1109/WF-IoT.2019.8767262 SP - 201 EP - 206 PB - Institute of Electrical and Electronics Engineers CY - New York ER - TY - JOUR A1 - Seiffert, Martin A1 - Holstein, Flavio A1 - Schlosser, Rainer A1 - Schiller, Jochen T1 - Next generation cooperative wearables BT - generalized activity assessment computed fully distributed with in a wireless body area network JF - IEEE access : practical research, open solutions N2 - Currently available wearables are usually based on a single sensor node with integrated capabilities for classifying different activities. The next generation of cooperative wearables could be able to identify not only activities, but also to evaluate them qualitatively using the data of several sensor nodes attached to the body, to provide detailed feedback for the improvement of the execution. Especially within the application domains of sports and health-care, such immediate feedback to the execution of body movements is crucial for (re-) learning and improving motor skills. To enable such systems for a broad range of activities, generalized approaches for human motion assessment within sensor networks are required. In this paper, we present a generalized trainable activity assessment chain (AAC) for the online assessment of periodic human activity within a wireless body area network. AAC evaluates the execution of separate movements of a prior trained activity on a fine-grained quality scale. We connect qualitative assessment with human knowledge by projecting the AAC on the hierarchical decomposition of motion performed by the human body as well as establishing the assessment on a kinematic evaluation of biomechanically distinct motion fragments. We evaluate AAC in a real-world setting and show that AAC successfully delimits the movements of correctly performed activity from faulty executions and provides detailed reasons for the activity assessment. KW - Body sensor networks KW - distributed computing KW - motion analysis KW - physical activity assessment KW - biomechanics KW - multilevel systems Y1 - 2017 U6 - https://doi.org/10.1109/ACCESS.2017.2749005 SN - 2169-3536 VL - 5 SP - 16793 EP - 16807 PB - Institute of Electrical and Electronics Engineers CY - Piscataway ER - TY - THES A1 - Semmo, Amir T1 - Design and implementation of non-photorealistic rendering techniques for 3D geospatial data T1 - Design und Implementierung von nichtfotorealistischen Rendering-Techniken für 3D-Geodaten N2 - Geospatial data has become a natural part of a growing number of information systems and services in the economy, society, and people's personal lives. In particular, virtual 3D city and landscape models constitute valuable information sources within a wide variety of applications such as urban planning, navigation, tourist information, and disaster management. Today, these models are often visualized in detail to provide realistic imagery. However, a photorealistic rendering does not automatically lead to high image quality, with respect to an effective information transfer, which requires important or prioritized information to be interactively highlighted in a context-dependent manner. Approaches in non-photorealistic renderings particularly consider a user's task and camera perspective when attempting optimal expression, recognition, and communication of important or prioritized information. However, the design and implementation of non-photorealistic rendering techniques for 3D geospatial data pose a number of challenges, especially when inherently complex geometry, appearance, and thematic data must be processed interactively. Hence, a promising technical foundation is established by the programmable and parallel computing architecture of graphics processing units. This thesis proposes non-photorealistic rendering techniques that enable both the computation and selection of the abstraction level of 3D geospatial model contents according to user interaction and dynamically changing thematic information. To achieve this goal, the techniques integrate with hardware-accelerated rendering pipelines using shader technologies of graphics processing units for real-time image synthesis. The techniques employ principles of artistic rendering, cartographic generalization, and 3D semiotics—unlike photorealistic rendering—to synthesize illustrative renditions of geospatial feature type entities such as water surfaces, buildings, and infrastructure networks. In addition, this thesis contributes a generic system that enables to integrate different graphic styles—photorealistic and non-photorealistic—and provide their seamless transition according to user tasks, camera view, and image resolution. Evaluations of the proposed techniques have demonstrated their significance to the field of geospatial information visualization including topics such as spatial perception, cognition, and mapping. In addition, the applications in illustrative and focus+context visualization have reflected their potential impact on optimizing the information transfer regarding factors such as cognitive load, integration of non-realistic information, visualization of uncertainty, and visualization on small displays. N2 - Geodaten haben sich zu einem natürlichen Bestandteil in einer steigenden Zahl von Informationssystemen und -diensten in der Wirtschaft, Gesellschaft und im Privatleben entwickelt. Virtuelle 3D-Stadt- und Landschaftsmodelle stellen hierbei insbesondere wertvolle Informationsquellen in einer Vielzahl von Anwendungen dar, wie z. B. in der Stadtplanung, Navigation, Touristeninformation und im Katastrophenschutz. Heutzutage werden diese Modelle oftmals detailliert dargestellt, um ein möglichst realistisches Bild zu vermitteln. Jedoch führt eine fotorealistische Darstellung, hinsichtlich einem effektiven Informationstransfer zum Betrachter, nicht zwangsläufig zu einer hohen Bildqualität, welche eine interaktive und kontextsensitive Hervorhebung von wichtigen oder priorisierten Informationen erfordert. Ansätze in der nichtfotorealistischen Bildsynthese berücksichtigen insbesondere die Aufgabe eines Nutzers und Kameraperspektive, um Aspekte der Expressivität, Wahrnehmung und Kommunikation von wichtigen oder priorisierten Informationen zu optimieren. Das Design und die Umsetzung von Techniken der nichtfotorealistischen Bildsynthese für 3D-Geodaten sind jedoch mit einer Vielzahl von Herausforderungen konfrontiert, besonders dann, wenn die Geometrie, das Erscheinungsbild und thematische Daten interaktiv verarbeitet werden müssen. Infolgedessen stellt die programmierbare Architektur und parallelisierte Datenverarbeitung von Grafik-prozessoren eine vielversprechende technische Grundlage zur Verfügung. Diese Arbeit präsentiert Techniken der nichtfotorealistischen Bildsynthese, die den Abstraktionsgrad von Inhalten raumbezogener 3D-Modelle, entsprechend der Nutzerinteraktion und dynamisch-veränderbaren thematischen Informationen, berechnet und auswählt. Hierzu sind die vorgestellten Techniken in die hardwarebeschleunigte Rendering-Pipeline integriert, unter Verwendung der Shader-Technologie von Grafikprozessoren, um eine Echtzeit-Bildsynthese zu gewährleisten. Dabei werden Prinzipien der künstlerischen Darstellung, Aspekte der kartographischen Generalisierung sowie 3D Semiotik verwendet—im Gegensatz zur fotorealistischen Bildsynthese—um illustrative Darstellungen von raumbezogenen Feature-Typ-Entitäten zu synthetisieren, z. B. von Wasserflächen, Gebäuden und Infrastrukturnetzen. Darüber hinaus stellt diese Arbeit ein generisches System vor, welches die Integration verschiedener Grafikstile—fotorealistisch und nichtfotorealistisch—und ihren nahtlosen Übergang, entsprechend von Nutzeraufgaben, Kameraansichten und Bildauflösungen, ermöglicht. Evaluierungen der in dieser Arbeit vorgestellten Techniken haben ihre Bedeutung im Bereich der Informationsvisualisierung von raumbezogenen Daten aufgezeigt, einschließlich Themengebiete der räumlichen Wahrnehmung, Kognition und Kartierung. Darüber hinaus haben Anwendungen im Bereich der illustrativen Visualisierung und Fokus-&-Kontext Visualisierung den potentiellen Einfluss dieser Techniken, in Bezug auf die Optimierung des Informationstransfers zum Nutzer, demonstriert, z. B. hinsichtlich der kognitiven Last, der Integration nichtrealistischer Informationen, der Visualisierung von Unsicherheiten und der Visualisierung auf kleinen Bildschirmen. KW - non-photorealistic rendering KW - geospatial data KW - 3D visualization KW - GPU KW - image processing KW - stylization KW - 3D semiotics KW - cartographic design KW - Nichtfotorealistische Bildsynthese KW - Geodaten KW - 3D Visualisierung KW - GPU KW - Bildverarbeitung KW - Stilisierung KW - 3D Semiotik KW - Kartografisches Design Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-99525 ER - TY - JOUR A1 - Semmo, Amir A1 - Döllner, Jürgen Roland Friedrich T1 - Interactive image filtering for level-of-abstraction texturing of virtual 3D scenes JF - Computers & graphics : CAG ; an international journal of applications in computer graphics N2 - Texture mapping is a key technology in computer graphics. For the visual design of 3D scenes, in particular, effective texturing depends significantly on how important contents are expressed, e.g., by preserving global salient structures, and how their depiction is cognitively processed by the user in an application context. Edge-preserving image filtering is one key approach to address these concerns. Much research has focused on applying image filters in a post-process stage to generate artistically stylized depictions. However, these approaches generally do not preserve depth cues, which are important for the perception of 3D visualization (e.g., texture gradient). To this end, filtering is required that processes texture data coherently with respect to linear perspective and spatial relationships. In this work, we present an approach for texturing 3D scenes with perspective coherence by arbitrary image filters. We propose decoupled deferred texturing with (1) caching strategies to interactively perform image filtering prior to texture mapping and (2) for each mipmap level separately to enable a progressive level of abstraction, using (3) direct interaction interfaces to parameterize the visualization according to spatial, semantic, and thematic data. We demonstrate the potentials of our method by several applications using touch or natural language inputs to serve the different interests of users in specific information, including illustrative visualization, focus+context visualization, geometric detail removal, and semantic depth of field. The approach supports frame-to-frame coherence, order-independent transparency, multitexturing, and content-based filtering. In addition, it seamlessly integrates into real-time rendering pipelines and is extensible for custom interaction techniques. (C) 2015 Elsevier Ltd. All rights reserved. KW - Image filtering KW - Level of abstraction KW - Texturing KW - Virtual 3D scenes KW - Visualization KW - Interaction Y1 - 2015 U6 - https://doi.org/10.1016/j.cag.2015.02.001 SN - 0097-8493 SN - 1873-7684 VL - 52 SP - 181 EP - 198 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Semmo, Amir A1 - Hildebrandt, Dieter A1 - Trapp, Matthias A1 - Döllner, Jürgen Roland Friedrich T1 - Concepts for cartography-oriented visualization of virtual 3D city models JF - Photogrammetrie, Fernerkundung, Geoinformation N2 - Virtual 3D city models serve as an effective medium with manifold applications in geoinformation systems and services. To date, most 3D city models are visualized using photorealistic graphics. But an effective communication of geoinformation significantly depends on how important information is designed and cognitively processed in the given application context. One possibility to visually emphasize important information is based on non-photorealistic rendering, which comprehends artistic depiction styles and is characterized by its expressiveness and communication aspects. However, a direct application of non-photorealistic rendering techniques primarily results in monotonic visualization that lacks cartographic design aspects. In this work, we present concepts for cartography-oriented visualization of virtual 3D city models. These are based on coupling non-photorealistic rendering techniques and semantics-based information for a user, context, and media-dependent representation of thematic information. This work highlights challenges for cartography-oriented visualization of 3D geovirtual environments, presents stylization techniques and discusses their applications and ideas for a standardized visualization. In particular, the presented concepts enable a real-time and dynamic visualization of thematic geoinformation. KW - 3D city models KW - cartography-oriented visualization KW - style description languages KW - real-time rendering Y1 - 2012 U6 - https://doi.org/10.1127/1432-8364/2012/0131 SN - 1432-8364 IS - 4 SP - 455 EP - 465 PB - Schweizerbart CY - Stuttgart ER - TY - JOUR A1 - Semmo, Amir A1 - Trapp, Matthias A1 - Jobst, Markus A1 - Döllner, Jürgen Roland Friedrich T1 - Cartography-Oriented Design of 3D Geospatial Information Visualization - Overview and Techniques JF - The cartographic journal N2 - In economy, society and personal life map-based interactive geospatial visualization becomes a natural element of a growing number of applications and systems. The visualization of 3D geospatial information, however, raises the question how to represent the information in an effective way. Considerable research has been done in technology-driven directions in the fields of cartography and computer graphics (e.g., design principles, visualization techniques). Here, non-photorealistic rendering (NPR) represents a promising visualization category - situated between both fields - that offers a large number of degrees for the cartography-oriented visual design of complex 2D and 3D geospatial information for a given application context. Still today, however, specifications and techniques for mapping cartographic design principles to the state-of-the-art rendering pipeline of 3D computer graphics remain to be explored. This paper revisits cartographic design principles for 3D geospatial visualization and introduces an extended 3D semiotic model that complies with the general, interactive visualization pipeline. Based on this model, we propose NPR techniques to interactively synthesize cartographic renditions of basic feature types, such as terrain, water, and buildings. In particular, it includes a novel iconification concept to seamlessly interpolate between photorealistic and cartographic representations of 3D landmarks. Our work concludes with a discussion of open challenges in this field of research, including topics, such as user interaction and evaluation. KW - 3D information visualization KW - 3D semiotic model KW - cartographic design KW - user interaction KW - real-time rendering Y1 - 2015 U6 - https://doi.org/10.1080/00087041.2015.1119462 SN - 0008-7041 SN - 1743-2774 VL - 52 IS - 2 SP - 95 EP - 106 PB - Routledge, Taylor & Francis Group CY - Leeds ER - TY - JOUR A1 - Semmo, Amir A1 - Trapp, Matthias A1 - Kyprianidis, Jan Eric A1 - Döllner, Jürgen Roland Friedrich T1 - Interactive visualization of generalized virtual 3D city models using level-of-abstraction transitions JF - Computer graphics forum : journal of the European Association for Computer Graphics N2 - Virtual 3D city models play an important role in the communication of complex geospatial information in a growing number of applications, such as urban planning, navigation, tourist information, and disaster management. In general, homogeneous graphic styles are used for visualization. For instance, photorealism is suitable for detailed presentations, and non-photorealism or abstract stylization is used to facilitate guidance of a viewer's gaze to prioritized information. However, to adapt visualization to different contexts and contents and to support saliency-guided visualization based on user interaction or dynamically changing thematic information, a combination of different graphic styles is necessary. Design and implementation of such combined graphic styles pose a number of challenges, specifically from the perspective of real-time 3D visualization. In this paper, the authors present a concept and an implementation of a system that enables different presentation styles, their seamless integration within a single view, and parametrized transitions between them, which are defined according to tasks, camera view, and image resolution. The paper outlines potential usage scenarios and application fields together with a performance evaluation of the implementation. Y1 - 2012 U6 - https://doi.org/10.1111/j.1467-8659.2012.03081.x SN - 0167-7055 VL - 31 IS - 3 SP - 885 EP - 894 PB - Wiley-Blackwell CY - Hoboken ER - TY - GEN A1 - Serth, Sebastian A1 - Podlesny, Nikolai A1 - Bornstein, Marvin A1 - Lindemann, Jan A1 - Latt, Johanna A1 - Selke, Jan A1 - Schlosser, Rainer A1 - Boissier, Martin A1 - Uflacker, Matthias T1 - An interactive platform to simulate dynamic pricing competition on online marketplaces T2 - 2017 IEEE 21st International Enterprise Distributed Object Computing Conference (EDOC) N2 - E-commerce marketplaces are highly dynamic with constant competition. While this competition is challenging for many merchants, it also provides plenty of opportunities, e.g., by allowing them to automatically adjust prices in order to react to changing market situations. For practitioners however, testing automated pricing strategies is time-consuming and potentially hazardously when done in production. Researchers, on the other side, struggle to study how pricing strategies interact under heavy competition. As a consequence, we built an open continuous time framework to simulate dynamic pricing competition called Price Wars. The microservice-based architecture provides a scalable platform for large competitions with dozens of merchants and a large random stream of consumers. Our platform stores each event in a distributed log. This allows to provide different performance measures enabling users to compare profit and revenue of various repricing strategies in real-time. For researchers, price trajectories are shown which ease evaluating mutual price reactions of competing strategies. Furthermore, merchants can access historical marketplace data and apply machine learning. By providing a set of customizable, artificial merchants, users can easily simulate both simple rule-based strategies as well as sophisticated data-driven strategies using demand learning to optimize their pricing strategies. Y1 - 2017 SN - 978-1-5090-3045-3 U6 - https://doi.org/10.1109/EDOC.2017.17 SN - 2325-6354 SP - 61 EP - 66 PB - Institute of Electrical and Electronics Engineers CY - New York ER - TY - THES A1 - Shaabani, Nuhad T1 - On discovering and incrementally updating inclusion dependencies N2 - In today's world, many applications produce large amounts of data at an enormous rate. Analyzing such datasets for metadata is indispensable for effectively understanding, storing, querying, manipulating, and mining them. Metadata summarizes technical properties of a dataset which rang from basic statistics to complex structures describing data dependencies. One type of dependencies is inclusion dependency (IND), which expresses subset-relationships between attributes of datasets. Therefore, inclusion dependencies are important for many data management applications in terms of data integration, query optimization, schema redesign, or integrity checking. So, the discovery of inclusion dependencies in unknown or legacy datasets is at the core of any data profiling effort. For exhaustively detecting all INDs in large datasets, we developed S-indd++, a new algorithm that eliminates the shortcomings of existing IND-detection algorithms and significantly outperforms them. S-indd++ is based on a novel concept for the attribute clustering for efficiently deriving INDs. Inferring INDs from our attribute clustering eliminates all redundant operations caused by other algorithms. S-indd++ is also based on a novel partitioning strategy that enables discording a large number of candidates in early phases of the discovering process. Moreover, S-indd++ does not require to fit a partition into the main memory--this is a highly appreciable property in the face of ever-growing datasets. S-indd++ reduces up to 50% of the runtime of the state-of-the-art approach. None of the approach for discovering INDs is appropriate for the application on dynamic datasets; they can not update the INDs after an update of the dataset without reprocessing it entirely. To this end, we developed the first approach for incrementally updating INDs in frequently changing datasets. We achieved that by reducing the problem of incrementally updating INDs to the incrementally updating the attribute clustering from which all INDs are efficiently derivable. We realized the update of the clusters by designing new operations to be applied to the clusters after every data update. The incremental update of INDs reduces the time of the complete rediscovery by up to 99.999%. All existing algorithms for discovering n-ary INDs are based on the principle of candidate generation--they generate candidates and test their validity in the given data instance. The major disadvantage of this technique is the exponentially growing number of database accesses in terms of SQL queries required for validation. We devised Mind2, the first approach for discovering n-ary INDs without candidate generation. Mind2 is based on a new mathematical framework developed in this thesis for computing the maximum INDs from which all other n-ary INDs are derivable. The experiments showed that Mind2 is significantly more scalable and effective than hypergraph-based algorithms. N2 - Viele Anwendungen produzieren mit schnellem Tempo große Datenmengen. Die Profilierung solcher Datenmengen nach ihren Metadaten ist unabdingbar für ihre effektive Verwaltung und ihre Analyse. Metadaten fassen technische Eigenschaften einer Datenmenge zusammen, welche von einfachen Statistiken bis komplexe und Datenabhängigkeiten beschreibende Strukturen umfassen. Eine Form solcher Abhängigkeiten sind Inklusionsabhängigkeiten (INDs), die Teilmengenbeziehungen zwischen Attributen der Datenmengen ausdrücken. Dies macht INDs wichtig für viele Anwendungen wie Datenintegration, Anfragenoptimierung, Schemaentwurf und Integritätsprüfung. Somit ist die Entdeckung von INDs in unbekannten Datenmengen eine zentrale Aufgabe der Datenprofilierung. Ich entwickelte einen neuen Algorithmus namens S-indd++ für die IND-Entdeckung in großen Datenmengen. S-indd++ beseitigt die Defizite existierender Algorithmen für die IND-Entdeckung und somit ist er performanter. S-indd++ berechnet INDs sehr effizient basierend auf einem neuen Clustering der Attribute. S-indd++ wendet auch eine neue Partitionierungsmethode an, die das Verwerfen einer großen Anzahl von Kandidaten in früheren Phasen des Entdeckungsprozesses ermöglicht. Außerdem setzt S-indd++ nicht voraus, dass eine Datenpartition komplett in den Hauptspeicher passen muss. S-indd++ reduziert die Laufzeit der IND-Entdeckung um bis 50 %. Keiner der IND-Entdeckungsalgorithmen ist geeignet für die Anwendung auf dynamischen Daten. Zu diesem Zweck entwickelte ich das erste Verfahren für das inkrementelle Update von INDs in häufig geänderten Daten. Ich erreichte dies bei der Reduzierung des Problems des inkrementellen Updates von INDs auf dem inkrementellen Update des Attribute-Clustering, von dem INDs effizient ableitbar sind. Ich realisierte das Update der Cluster beim Entwurf von neuen Operationen, die auf den Clustern nach jedem Update der Daten angewendet werden. Das inkrementelle Update von INDs reduziert die Zeit der statischen IND-Entdeckung um bis 99,999 %. Alle vorhandenen Algorithmen für die n-ary-IND-Entdeckung basieren auf dem Prinzip der Kandidatengenerierung. Der Hauptnachteil dieser Methode ist die exponentiell wachsende Anzahl der SQL-Anfragen, die für die Validierung der Kandidaten nötig sind. Zu diesem Zweck entwickelte ich Mind2, den ersten Algorithmus für n-ary-IND-Entdeckung ohne Kandidatengenerierung. Mind2 basiert auf einem neuen mathematischen Framework für die Berechnung der maximalen INDs, von denen alle anderen n-ary-INDs ableitbar sind. Die Experimente zeigten, dass Mind2 wesentlich skalierbarer und leistungsfähiger ist als die auf Hypergraphen basierenden Algorithmen. T2 - Beitrag zur Entdeckung und inkrementellen Aktualisierung von Inklusionsabhängigkeiten KW - Inclusion Dependency KW - Data Profiling KW - Data Mining KW - Algorithms KW - Inclusion Dependency Discovery KW - Incrementally Inclusion Dependencies Discovery KW - Metadata Discovery KW - S-indd++ KW - Mind2 KW - Change Data Capture KW - Incremental Discovery KW - Big Data KW - Data Integration KW - Foreign Keys KW - Dynamic Data KW - Foreign Keys Discovery KW - Data Profiling KW - Data Mining KW - Algorithmen KW - Inklusionsabhängigkeiten KW - Inklusionsabhängigkeiten Entdeckung KW - Datenintegration KW - Metadaten Entdeckung Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-471862 ER - TY - JOUR A1 - Shekhar, Sumit A1 - Reimann, Max A1 - Mayer, Maximilian A1 - Semmo, Amir A1 - Pasewaldt, Sebastian A1 - Döllner, Jürgen A1 - Trapp, Matthias T1 - Interactive photo editing on smartphones via intrinsic decomposition JF - Computer graphics forum : journal of the European Association for Computer Graphics N2 - Intrinsic decomposition refers to the problem of estimating scene characteristics, such as albedo and shading, when one view or multiple views of a scene are provided. The inverse problem setting, where multiple unknowns are solved given a single known pixel-value, is highly under-constrained. When provided with correlating image and depth data, intrinsic scene decomposition can be facilitated using depth-based priors, which nowadays is easy to acquire with high-end smartphones by utilizing their depth sensors. In this work, we present a system for intrinsic decomposition of RGB-D images on smartphones and the algorithmic as well as design choices therein. Unlike state-of-the-art methods that assume only diffuse reflectance, we consider both diffuse and specular pixels. For this purpose, we present a novel specularity extraction algorithm based on a multi-scale intensity decomposition and chroma inpainting. At this, the diffuse component is further decomposed into albedo and shading components. We use an inertial proximal algorithm for non-convex optimization (iPiano) to ensure albedo sparsity. Our GPU-based visual processing is implemented on iOS via the Metal API and enables interactive performance on an iPhone 11 Pro. Further, a qualitative evaluation shows that we are able to obtain high-quality outputs. Furthermore, our proposed approach for specularity removal outperforms state-of-the-art approaches for real-world images, while our albedo and shading layer decomposition is faster than the prior work at a comparable output quality. Manifold applications such as recoloring, retexturing, relighting, appearance editing, and stylization are shown, each using the intrinsic layers obtained with our method and/or the corresponding depth data. KW - CCS Concepts KW - center dot Computing KW - methodologie KW - Image-based rendering KW - Image KW - processing KW - Computational photography Y1 - 2021 U6 - https://doi.org/10.1111/cgf.142650 SN - 0167-7055 SN - 1467-8659 VL - 40 SP - 497 EP - 510 PB - Blackwell CY - Oxford ER - TY - GEN A1 - Sianipar, Johannes Harungguan A1 - Willems, Christian A1 - Meinel, Christoph T1 - Virtual machine integrity verification in Crowd-Resourcing Virtual Laboratory T2 - 2018 IEEE 11th Conference on Service-Oriented Computing and Applications (SOCA) N2 - In cloud computing, users are able to use their own operating system (OS) image to run a virtual machine (VM) on a remote host. The virtual machine OS is started by the user using some interfaces provided by a cloud provider in public or private cloud. In peer to peer cloud, the VM is started by the host admin. After the VM is running, the user could get a remote access to the VM to install, configure, and run services. For the security reasons, the user needs to verify the integrity of the running VM, because a malicious host admin could modify the image or even replace the image with a similar image, to be able to get sensitive data from the VM. We propose an approach to verify the integrity of a running VM on a remote host, without using any specific hardware such as Trusted Platform Module (TPM). Our approach is implemented on a Linux platform where the kernel files (vmlinuz and initrd) could be replaced with new files, while the VM is running. kexec is used to reboot the VM with the new kernel files. The new kernel has secret codes that will be used to verify whether the VM was started using the new kernel files. The new kernel is used to further measuring the integrity of the running VM. KW - Virtual Machine KW - Integrity Verification KW - Crowd-Resourcing KW - Cloud Computing Y1 - 2019 SN - 978-1-5386-9133-5 U6 - https://doi.org/10.1109/SOCA.2018.00032 SN - 2163-2871 SP - 169 EP - 176 PB - IEEE CY - New York ER - TY - JOUR A1 - Siddiqi, Muhammad Ali A1 - Dörr, Christian A1 - Strydis, Christos T1 - IMDfence BT - architecting a secure protocol for implantable medical devices JF - IEEE access N2 - Over the past decade, focus on the security and privacy aspects of implantable medical devices (IMDs) has intensified, driven by the multitude of cybersecurity vulnerabilities found in various existing devices. However, due to their strict computational, energy and physical constraints, conventional security protocols are not directly applicable to IMDs. Custom-tailored schemes have been proposed instead which, however, fail to cover the full spectrum of security features that modern IMDs and their ecosystems so critically require. In this paper we propose IMDfence, a security protocol for IMD ecosystems that provides a comprehensive yet practical security portfolio, which includes availability, non-repudiation, access control, entity authentication, remote monitoring and system scalability. The protocol also allows emergency access that results in the graceful degradation of offered services without compromising security and patient safety. The performance of the security protocol as well as its feasibility and impact on modern IMDs are extensively analyzed and evaluated. We find that IMDfence achieves the above security requirements at a mere less than 7% increase in total IMD energy consumption, and less than 14 ms and 9 kB increase in system delay and memory footprint, respectively. KW - protocols KW - implants KW - authentication KW - ecosystems KW - remote monitoring KW - scalability KW - authentication protocol KW - battery-depletion attack KW - battery KW - DoS KW - denial-of-service attack KW - IMD KW - implantable medical device KW - non-repudiation KW - smart card KW - zero-power defense Y1 - 2020 U6 - https://doi.org/10.1109/ACCESS.2020.3015686 SN - 2169-3536 VL - 8 SP - 147948 EP - 147964 PB - Institute of Electrical and Electronics Engineers CY - Piscataway ER - TY - JOUR A1 - Sigel, Keith Magnus A1 - Swartz, Talia H. A1 - Golden, Eddye A1 - Paranjpe, Ishan A1 - Somani, Sulaiman A1 - Richter, Felix A1 - De Freitas, Jessica K. A1 - Miotto, Riccardo A1 - Zhao, Shan A1 - Polak, Paz A1 - Mutetwa, Tinaye A1 - Factor, Stephanie A1 - Mehandru, Saurabh A1 - Mullen, Michael A1 - Cossarini, Francesca A1 - Böttinger, Erwin A1 - Fayad, Zahi A1 - Merad, Miriam A1 - Gnjatic, Sacha A1 - Aberg, Judith A1 - Charney, Alexander A1 - Nadkarni, Girish A1 - Glicksberg, Benjamin S. T1 - Coronavirus 2019 and people living with human immunodeficiency virus BT - outcomes for hospitalized patients in New York City JF - Clinical infectious diseases : electronic edition N2 - Background: There are limited data regarding the clinical impact of coronavirus disease 2019 (COVID-19) on people living with human immunodeficiency virus (PLWH). In this study, we compared outcomes for PLWH with COVID-19 to a matched comparison group. Methods: We identified 88 PLWH hospitalized with laboratory-confirmed COVID-19 in our hospital system in New York City between 12 March and 23 April 2020. We collected data on baseline clinical characteristics, laboratory values, HIV status, treatment, and outcomes from this group and matched comparators (1 PLWH to up to 5 patients by age, sex, race/ethnicity, and calendar week of infection). We compared clinical characteristics and outcomes (death, mechanical ventilation, hospital discharge) for these groups, as well as cumulative incidence of death by HIV status. Results: Patients did not differ significantly by HIV status by age, sex, or race/ethnicity due to the matching algorithm. PLWH hospitalized with COVID-19 had high proportions of HIV virologic control on antiretroviral therapy. PLWH had greater proportions of smoking (P < .001) and comorbid illness than uninfected comparators. There was no difference in COVID-19 severity on admission by HIV status (P = .15). Poor outcomes for hospitalized PLWH were frequent but similar to proportions in comparators; 18% required mechanical ventilation and 21% died during follow-up (compared with 23% and 20%, respectively). There was similar cumulative incidence of death over time by HIV status (P = .94). Conclusions: We found no differences in adverse outcomes associated with HIV infection for hospitalized COVID-19 patients compared with a demographically similar patient group. KW - human immunodeficiency virus KW - coronavirus 2019 KW - severe acute respiratory KW - syndrome coronavirus 2 Y1 - 2020 U6 - https://doi.org/10.1093/cid/ciaa880 SN - 1058-4838 SN - 1537-6591 VL - 71 IS - 11 SP - 2933 EP - 2938 PB - Oxford Univ. Press CY - Cary, NC ER - TY - JOUR A1 - Sinn, Ludwig R. A1 - Giese, Sven Hans-Joachim A1 - Stuiver, Marchel A1 - Rappsilber, Juri T1 - Leveraging parameter dependencies in high-field asymmetric waveform ion-mobility spectrometry and size exclusion chromatography for proteome-wide cross-linking mass spectrometry JF - Analytical chemistry : the authoritative voice of the analytical community N2 - Ion-mobility spectrometry shows great promise to tackle analytically challenging research questions by adding another separation dimension to liquid chromatography-mass spectrometry. The understanding of how analyte properties influence ion mobility has increased through recent studies, but no clear rationale for the design of customized experimental settings has emerged. Here, we leverage machine learning to deepen our understanding of field asymmetric waveform ion-mobility spectrometry for the analysis of cross-linked peptides. Knowing that predominantly m/z and then the size and charge state of an analyte influence the separation, we found ideal compensation voltages correlating with the size exclusion chromatography fraction number. The effect of this relationship on the analytical depth can be substantial as exploiting it allowed us to almost double unique residue pair detections in a proteome-wide cross-linking experiment. Other applications involving liquid- and gas-phase separation may also benefit from considering such parameter dependencies. Y1 - 2022 U6 - https://doi.org/10.1021/acs.analchem.1c04373 SN - 0003-2700 SN - 1520-6882 VL - 94 IS - 11 SP - 4627 EP - 4634 PB - American Chemical Society CY - Columbus, Ohio ER - TY - THES A1 - Smirnov, Sergey T1 - Business process model abstraction T1 - Abstraktion von Geschäftsprozessmodellen N2 - Business process models are used within a range of organizational initiatives, where every stakeholder has a unique perspective on a process and demands the respective model. As a consequence, multiple process models capturing the very same business process coexist. Keeping such models in sync is a challenge within an ever changing business environment: once a process is changed, all its models have to be updated. Due to a large number of models and their complex relations, model maintenance becomes error-prone and expensive. Against this background, business process model abstraction emerged as an operation reducing the number of stored process models and facilitating model management. Business process model abstraction is an operation preserving essential process properties and leaving out insignificant details in order to retain information relevant for a particular purpose. Process model abstraction has been addressed by several researchers. The focus of their studies has been on particular use cases and model transformations supporting these use cases. This thesis systematically approaches the problem of business process model abstraction shaping the outcome into a framework. We investigate the current industry demand in abstraction summarizing it in a catalog of business process model abstraction use cases. The thesis focuses on one prominent use case where the user demands a model with coarse-grained activities and overall process ordering constraints. We develop model transformations that support this use case starting with the transformations based on process model structure analysis. Further, abstraction methods considering the semantics of process model elements are investigated. First, we suggest how semantically related activities can be discovered in process models-a barely researched challenge. The thesis validates the designed abstraction methods against sets of industrial process models and discusses the method implementation aspects. Second, we develop a novel model transformation, which combined with the related activity discovery allows flexible non-hierarchical abstraction. In this way this thesis advocates novel model transformations that facilitate business process model management and provides the foundations for innovative tool support. N2 - Geschäftsprozessmodelle werden in einer Fülle organisatorischer Initiativen eingesetzt, wobei verschiedene Stakeholder individuelle Ansprüche an die Sicht auf den jeweiligen Prozess haben. Dies führt dazu, dass zu einem Geschäftsprozess eine Vielzahl unterschiedlicher Modelle existiert. In einer sich ständig verändernden Geschäftsumgebung ist es daher schwierig, diese Vielzahl von Modellen konsistent zu halten: Ändert sich sich ein Prozess, müssen alle Modelle, die ihn beschreiben, aktualisiert werden. Aufgrund der schieren Menge an Prozessmodellen und ihrer komplexen Beziehungen zueinander, erhöhen sich Aufwand und Kosten zur Pflege aller Modelle enorm. Vor diesem Hintergrund ermöglicht die Abstraktion von Geschäftsprozessmodellen, die Menge der Modelle zu reduzieren und damit ihre Verwaltung zu vereinfachen. Abstraktion von Geschäftsprozessmodellen bezeichnet eine Transformation eines Prozessmodells, so dass es für einen bestimmten Zweck besonders geeignet ist. Bei der Abstraktion von Geschäftsprozessen bleiben essentielle Eigenschaften eines Modells erhalten, während irrelevante Eigenschaften verworfen werden. Mehrere Studien stellen Prozessmodellabstraktion in den Fokus und konzentrieren sich auf konkrete Anwendungsfälle, für die sie geeignete Transformationen entwickelt haben. Diese Dissertation untersucht das Problem der Prozessmodellabstraktion und systematisiert die Lösung in einem Framework. Aktuelle Anforderungen der Industrie an die Abstraktion von Prozessmodellen wurden recherchiert und in einem Katalog von Anwendungsfällen zusammengefasst, von denen ein besonderer für die weiteren Untersuchungen ausgewählt wurde. In diesem Fall erwartet der Nutzer ein Modell niedrigeren Detailgrades, in welchem die Kontrollflussbeziehungen des Ursprungsmodells erhalten bleiben. Beginnend bei Modelltransformationen, die auf der Analyse der Prozessmodellstruktur aufbauen, entwickeln wir neuartige Abstraktionsoperationen zur Unterstützung dieses Anwendungsfalles. Darüber hinaus untersuchen wir Abstraktionsmethoden, welche die Semantik von Prozessmodellelementen berücksichtigen. Zum einen zeigen wir, wie Aktivitäten ermittelt werden können, die miteinander in semantischer Beziehung stehen - ein Problem, das bisher nur unzureichend betrachtet wurde. Die vorgeschlagenen Methoden werden mithilfe industrieller Prozessmodellsammlungen validiert und deren Umsetzung diskutiert. Zum anderen schlagen wir eine innovative Modelltransformation zur nicht-hierarchischen Abstraktion von Prozessmodellen vor. Dieser liegt die Ermittlung in Beziehung stehender Aktivitäten zugrunde. Demzufolge präsentiert diese Arbeit eine originäre Methode zur Prozessmodellabstraktion, die die Verwaltung von Geschäftsprozessmodellen vereinfacht und den Grundstein für innovative Softwarewerkzeuge legt. KW - Abstraktion KW - Prozess KW - Modell KW - Transformation KW - Komplexität KW - abstraction KW - process KW - model KW - transformation KW - complexity Y1 - 2011 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-60258 ER - TY - BOOK A1 - Smirnov, Sergey A1 - Reijers, Hajo A. A1 - Nugteren, Thijs A1 - Weske, Mathias T1 - Business process model abstraction : theory and practice N2 - Business process management aims at capturing, understanding, and improving work in organizations. The central artifacts are process models, which serve different purposes. Detailed process models are used to analyze concrete working procedures, while high-level models show, for instance, handovers between departments. To provide different views on process models, business process model abstraction has emerged. While several approaches have been proposed, a number of abstraction use case that are both relevant for industry and scientifically challenging are yet to be addressed. In this paper we systematically develop, classify, and consolidate different use cases for business process model abstraction. The reported work is based on a study with BPM users in the health insurance sector and validated with a BPM consultancy company and a large BPM vendor. The identified fifteen abstraction use cases reflect the industry demand. The related work on business process model abstraction is evaluated against the use cases, which leads to a research agenda. T3 - Technische Berichte des Hasso-Plattner-Instituts für Digital Engineering an der Universität Potsdam - 35 Y1 - 2010 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-41782 SN - 978-3-86956-054-0 PB - Universitätsverlag Potsdam CY - Potsdam ER - TY - BOOK A1 - Smirnov, Sergey A1 - Weidlich, Matthias A1 - Mendling, Jan A1 - Weske, Mathias T1 - Action patterns in business process models N2 - Business process management experiences a large uptake by the industry, and process models play an important role in the analysis and improvement of processes. While an increasing number of staff becomes involved in actual modeling practice, it is crucial to assure model quality and homogeneity along with providing suitable aids for creating models. In this paper we consider the problem of offering recommendations to the user during the act of modeling. Our key contribution is a concept for defining and identifying so-called action patterns - chunks of actions often appearing together in business processes. In particular, we specify action patterns and demonstrate how they can be identified from existing process model repositories using association rule mining techniques. Action patterns can then be used to suggest additional actions for a process model. Our approach is challenged by applying it to the collection of process models from the SAP Reference Model. N2 - Die zunehmende Bedeutung des Geschäftsprozessmanagements führt dazu, dass eine steigende Anzahl von Mitarbeitern eines Unternehmens mit der Erstellung von Prozessmodellen betraut ist. Um trotz dieser Tendenz die Qualität der Prozessmodelle, sowie ihre Homogenität sicherzustellen, sind entsprechende Modellierungshilfen unabdingbar. In diesem Bericht stellen wir einen Ansatz vor, welcher die Prozessmodellierung durch Empfehlungen unterstützt. Jene basieren auf sogenannten Aktionsmustern, welche typische Arbeitsblöcke darstellen. Neben der Definition dieser Aktionsmuster zeigen wir eine Methode zur Identifikation dieser Muster auf. Mittels Techniken der Assoziationsanalyse können die Muster automatisch aus einer Sammlung von Prozessmodellen extrahiert werden. Die Anwendbarkeit unseres Ansatzes wird durch eine Fallstudie auf Basis des SAP Referenzmodells illustriert. T3 - Technische Berichte des Hasso-Plattner-Instituts für Digital Engineering an der Universität Potsdam - 30 Y1 - 2009 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-33586 SN - 978-3-86956-009-0 PB - Universitätsverlag Potsdam CY - Potsdam ER - TY - BOOK A1 - Smirnov, Sergey A1 - Zamani Farahani, Armin A1 - Weske, Mathias T1 - State propagation in abstracted business processes N2 - Business process models are abstractions of concrete operational procedures that occur in the daily business of organizations. To cope with the complexity of these models, business process model abstraction has been introduced recently. Its goal is to derive from a detailed process model several abstract models that provide a high-level understanding of the process. While techniques for constructing abstract models are reported in the literature, little is known about the relationships between process instances and abstract models. In this paper we show how the state of an abstract activity can be calculated from the states of related, detailed process activities as they happen. The approach uses activity state propagation. With state uniqueness and state transition correctness we introduce formal properties that improve the understanding of state propagation. Algorithms to check these properties are devised. Finally, we use behavioral profiles to identify and classify behavioral inconsistencies in abstract process models that might occur, once activity state propagation is used. N2 - Geschäftsprozessmodelle sind Abstraktionen konkreter operationaler Vorgänge, die im täglichen Geschäftsablauf von Organisationen auftreten. Um die Komplexität solcher Modelle zu bewältigen, wurde die Geschäftsprozessmodelabstraktion eingeführt. Ziel ist dabei, von einem detaillierten Prozessmodel mehrere abstrakte Modelle abzuleiten, um so auf einer höheren Abstraktionsstufe ein Verständnis für den Prozess zu bekommen. Während viel in der Literatur über Techniken zur Konstruktion abstrakter Modelle berichtet wurde, ist wenig über die Beziehungen zwischen Prozessinstanzen und abstrakten Modellen bekannt. In dieser Arbeit zeigen wir, wie der Zustand einer abstrakten Aktivität aus den Zuständen ihrer entsprechenden detaillierten Prozessaktivitäten zur Laufzeit berechnet werden kann. Der Ansatz basiert dabei auf der Übertragung des Aktivitätszustands. Mit der Zustandseindeutigkeit und der Korrektheit der Zustandstransitionen führen wir formale Kriterien ein, die das Verständnis der Zustandsübertragung erleichtern. Zudem sind Algorithmen entwickelt worden, um diese Kriterien zu überprüfen. Außerdem nutzen wir Verhaltensprofile um Inkonsistenzen im Verhalten abstrakter Prozessmodelle zu identifizieren und zu klassifizieren, die auftreten können, wenn die Aktivitätszustände gemäß den Regeln abgebildet werden. T3 - Technische Berichte des Hasso-Plattner-Instituts für Digital Engineering an der Universität Potsdam - 47 KW - Abstraktion von Geschäftsprozessmodellen KW - Prozessinstanz KW - Propagation von Aktivitätsinstanzzuständen KW - business process model abstraction KW - process instance KW - activity instance state propagation Y1 - 2011 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-51480 SN - 978-3-86956-130-1 PB - Universitätsverlag Potsdam CY - Potsdam ER - TY - GEN A1 - Staubitz, Thomas A1 - Wilkins, Christian A1 - Hagedorn, Christiane A1 - Meinel, Christoph T1 - The Gamification of a MOOC Platform T2 - Proceedings of 2017 IEEE Global Engineering Education Conference (EDUCON) N2 - Massive Open Online Courses (MOOCs) have left their mark on the face of education during the recent years. At the Hasso Plattner Institute (HPI) in Potsdam, Germany, we are actively developing a MOOC platform, which provides our research with a plethora of e-learning topics, such as learning analytics, automated assessment, peer assessment, team-work, online proctoring, and gamification. We run several instances of this platform. On openHPI, we provide our own courses from within the HPI context. Further instances are openSAP, openWHO, and mooc.HOUSE, which is the smallest of these platforms, targeting customers with a less extensive course portfolio. In 2013, we started to work on the gamification of our platform. By now, we have implemented about two thirds of the features that we initially have evaluated as useful for our purposes. About a year ago we activated the implemented gamification features on mooc.HOUSE. Before activating the features on openHPI as well, we examined, and re-evaluated our initial considerations based on the data we collected so far and the changes in other contexts of our platforms. KW - MOOC KW - Gamification KW - e-learning KW - Massive Open Online Courses Y1 - 2017 SN - 978-1-5090-5467-1 U6 - https://doi.org/10.1109/EDUCON.2017.7942952 SN - 2165-9567 SP - 883 EP - 892 PB - IEEE CY - New York ER - TY - THES A1 - Steinert, Bastian T1 - Built-in recovery support for explorative programming T1 - Eingebaute Unterstützung für Wiederherstellungsbedürfnisse für unstrukturierte ergebnisoffene Programmieraufgaben BT - preserving immediate access to static and dynamic information of intermediate development states BT - Erhaltung des unmittelbaren Zugriffs auf statische und dynamische Informationen von Entwicklungszwischenständen N2 - This work introduces concepts and corresponding tool support to enable a complementary approach in dealing with recovery. Programmers need to recover a development state, or a part thereof, when previously made changes reveal undesired implications. However, when the need arises suddenly and unexpectedly, recovery often involves expensive and tedious work. To avoid tedious work, literature recommends keeping away from unexpected recovery demands by following a structured and disciplined approach, which consists of the application of various best practices including working only on one thing at a time, performing small steps, as well as making proper use of versioning and testing tools. However, the attempt to avoid unexpected recovery is both time-consuming and error-prone. On the one hand, it requires disproportionate effort to minimize the risk of unexpected situations. On the other hand, applying recommended practices selectively, which saves time, can hardly avoid recovery. In addition, the constant need for foresight and self-control has unfavorable implications. It is exhaustive and impedes creative problem solving. This work proposes to make recovery fast and easy and introduces corresponding support called CoExist. Such dedicated support turns situations of unanticipated recovery from tedious experiences into pleasant ones. It makes recovery fast and easy to accomplish, even if explicit commits are unavailable or tests have been ignored for some time. When mistakes and unexpected insights are no longer associated with tedious corrective actions, programmers are encouraged to change source code as a means to reason about it, as opposed to making changes only after structuring and evaluating them mentally. This work further reports on an implementation of the proposed tool support in the Squeak/Smalltalk development environment. The development of the tools has been accompanied by regular performance and usability tests. In addition, this work investigates whether the proposed tools affect programmers’ performance. In a controlled lab study, 22 participants improved the design of two different applications. Using a repeated measurement setup, the study examined the effect of providing CoExist on programming performance. The result of analyzing 88 hours of programming suggests that built-in recovery support as provided with CoExist positively has a positive effect on programming performance in explorative programming tasks. N2 - Diese Arbeit präsentiert Konzepte und die zugehörige Werkzeugunterstützung um einen komplementären Umgang mit Wiederherstellungsbedürfnissen zu ermöglichen. Programmierer haben Bedarf zur Wiederherstellung eines früheren Entwicklungszustandes oder Teils davon, wenn ihre Änderungen ungewünschte Implikationen aufzeigen. Wenn dieser Bedarf plötzlich und unerwartet auftritt, dann ist die notwendige Wiederherstellungsarbeit häufig mühsam und aufwendig. Zur Vermeidung mühsamer Arbeit empfiehlt die Literatur die Vermeidung von unerwarteten Wiederherstellungsbedürfnissen durch einen strukturierten und disziplinierten Programmieransatz, welcher die Verwendung verschiedener bewährter Praktiken vorsieht. Diese Praktiken sind zum Beispiel: nur an einer Sache gleichzeitig zu arbeiten, immer nur kleine Schritte auszuführen, aber auch der sachgemäße Einsatz von Versionskontroll- und Testwerkzeugen. Jedoch ist der Versuch des Abwendens unerwarteter Wiederherstellungsbedürfnisse sowohl zeitintensiv als auch fehleranfällig. Einerseits erfordert es unverhältnismäßig hohen Aufwand, das Risiko des Eintretens unerwarteter Situationen auf ein Minimum zu reduzieren. Andererseits ist eine zeitsparende selektive Ausführung der empfohlenen Praktiken kaum hinreichend, um Wiederherstellungssituationen zu vermeiden. Zudem bringt die ständige Notwendigkeit an Voraussicht und Selbstkontrolle Nachteile mit sich. Dies ist ermüdend und erschwert das kreative Problemlösen. Diese Arbeit schlägt vor, Wiederherstellungsaufgaben zu vereinfachen und beschleunigen, und stellt entsprechende Werkzeugunterstützung namens CoExist vor. Solche zielgerichtete Werkzeugunterstützung macht aus unvorhergesehenen mühsamen Wiederherstellungssituationen eine konstruktive Erfahrung. Damit ist Wiederherstellung auch dann leicht und schnell durchzuführen, wenn explizit gespeicherte Zwischenstände fehlen oder die Tests für einige Zeit ignoriert wurden. Wenn Fehler und unerwartete Ein- sichten nicht länger mit mühsamen Schadensersatz verbunden sind, fühlen sich Programmierer eher dazu ermutig, Quelltext zu ändern, um dabei darüber zu reflektieren, und nehmen nicht erst dann Änderungen vor, wenn sie diese gedanklich strukturiert und evaluiert haben. Diese Arbeit berichtet weiterhin von einer Implementierung der vorgeschlagenen Werkzeugunterstützung in der Squeak/Smalltalk Entwicklungsumgebung. Regelmäßige Tests von Laufzeitverhalten und Benutzbarkeit begleiteten die Entwicklung. Zudem prüft die Arbeit, ob sich die Verwendung der vorgeschlagenen Werkzeuge auf die Leistung der Programmierer auswirkt. In einem kontrollierten Experiment, verbesserten 22 Teilnehmer den Aufbau von zwei verschiedenen Anwendungen. Unter der Verwendung einer Versuchsanordnung mit wiederholter Messung, ermittelte die Studie die Auswirkung von CoExist auf die Programmierleistung. Das Ergebnis der Analyse von 88 Programmierstunden deutet darauf hin, dass sich eingebaute Werkzeugunterstützung für Wiederherstellung, wie sie mit CoExist bereitgestellt wird, positiv bei der Bearbeitung von unstrukturierten ergebnisoffenen Programmieraufgaben auswirkt. KW - Softwaretechnik KW - Entwicklungswerkzeuge KW - Versionierung KW - Testen KW - software engineering KW - development tools KW - versioning KW - testing Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-71305 ER - TY - JOUR A1 - Steinert, Bastian A1 - Thamsen, Lauritz A1 - Felgentreff, Tim A1 - Hirschfeld, Robert T1 - Object Versioning to Support Recovery Needs Using Proxies to Preserve Previous Development States in Lively JF - ACM SIGPLAN notices N2 - We present object versioning as a generic approach to preserve access to previous development and application states. Version-aware references can manage the modifications made to the target object and record versions as desired. Such references can be provided without modifications to the virtual machine. We used proxies to implement the proposed concepts and demonstrate the Lively Kernel running on top of this object versioning layer. This enables Lively users to undo the effects of direct manipulation and other programming actions. KW - Programming Environments KW - Object Versioning KW - CoExist KW - JavaScript KW - Lively Kernel Y1 - 2015 U6 - https://doi.org/10.1145/2661088.2661093 SN - 0362-1340 SN - 1558-1160 VL - 50 IS - 2 SP - 113 EP - 124 PB - Association for Computing Machinery CY - New York ER - TY - THES A1 - Steinmetz, Nadine T1 - Context-aware semantic analysis of video metadata T1 - Kontextbezogene, semantische Analyse von Videometadaten N2 - Im Vergleich zu einer stichwortbasierten Suche ermöglicht die semantische Suche ein präziseres und anspruchsvolleres Durchsuchen von (Web)-Dokumenten, weil durch die explizite Semantik Mehrdeutigkeiten von natürlicher Sprache vermieden und semantische Beziehungen in das Suchergebnis einbezogen werden können. Eine semantische, Entitäten-basierte Suche geht von einer Anfrage mit festgelegter Bedeutung aus und liefert nur Dokumente, die mit dieser Entität annotiert sind als Suchergebnis. Die wichtigste Voraussetzung für eine Entitäten-zentrierte Suche stellt die Annotation der Dokumente im Archiv mit Entitäten und Kategorien dar. Textuelle Informationen werden analysiert und mit den entsprechenden Entitäten und Kategorien versehen, um den Inhalt semantisch erschließen zu können. Eine manuelle Annotation erfordert Domänenwissen und ist sehr zeitaufwendig. Die semantische Annotation von Videodokumenten erfordert besondere Aufmerksamkeit, da inhaltsbasierte Metadaten von Videos aus verschiedenen Quellen stammen, verschiedene Eigenschaften und Zuverlässigkeiten besitzen und daher nicht wie Fließtext behandelt werden können. Die vorliegende Arbeit stellt einen semantischen Analyseprozess für Video-Metadaten vor. Die Eigenschaften der verschiedenen Metadatentypen werden analysiert und ein Konfidenzwert ermittelt. Dieser Wert spiegelt die Korrektheit und die wahrscheinliche Mehrdeutigkeit eines Metadatums wieder. Beginnend mit dem Metadatum mit dem höchsten Konfidenzwert wird der Analyseprozess innerhalb eines Kontexts in absteigender Reihenfolge des Konfidenzwerts durchgeführt. Die bereits analysierten Metadaten dienen als Referenzpunkt für die weiteren Analysen. So kann eine möglichst korrekte Analyse der heterogen strukturierten Daten eines Kontexts sichergestellt werden. Am Ende der Analyse eines Metadatums wird die für den Kontext relevanteste Entität aus einer Liste von Kandidaten identifiziert - das Metadatum wird disambiguiert. Hierfür wurden verschiedene Disambiguierungsalgorithmen entwickelt, die Beschreibungstexte und semantische Beziehungen der Entitätenkandidaten zum gegebenen Kontext in Betracht ziehen. Der Kontext für die Disambiguierung wird für jedes Metadatum anhand der Eigenschaften und Konfidenzwerte zusammengestellt. Der vorgestellte Analyseprozess ist an zwei Hypothesen angelehnt: Um die Analyseergebnisse verbessern zu können, sollten die Metadaten eines Kontexts in absteigender Reihenfolge ihres Konfidenzwertes verarbeitet werden und die Kontextgrenzen von Videometadaten sollten durch Segmentgrenzen definiert werden, um möglichst Kontexte mit kohärentem Inhalt zu erhalten. Durch ausführliche Evaluationen konnten die gestellten Hypothesen bestätigt werden. Der Analyseprozess wurden gegen mehrere State-of-the-Art Methoden verglichen und erzielt verbesserte Ergebnisse in Bezug auf Recall und Precision, besonders für Metadaten, die aus weniger zuverlässigen Quellen stammen. Der Analyseprozess ist Teil eines Videoanalyse-Frameworks und wurde bereits erfolgreich in verschiedenen Projekten eingesetzt. N2 - The Semantic Web provides information contained in the World Wide Web as machine-readable facts. In comparison to a keyword-based inquiry, semantic search enables a more sophisticated exploration of web documents. By clarifying the meaning behind entities, search results are more precise and the semantics simultaneously enable an exploration of semantic relationships. However, unlike keyword searches, a semantic entity-focused search requires that web documents are annotated with semantic representations of common words and named entities. Manual semantic annotation of (web) documents is time-consuming; in response, automatic annotation services have emerged in recent years. These annotation services take continuous text as input, detect important key terms and named entities and annotate them with semantic entities contained in widely used semantic knowledge bases, such as Freebase or DBpedia. Metadata of video documents require special attention. Semantic analysis approaches for continuous text cannot be applied, because information of a context in video documents originates from multiple sources possessing different reliabilities and characteristics. This thesis presents a semantic analysis approach consisting of a context model and a disambiguation algorithm for video metadata. The context model takes into account the characteristics of video metadata and derives a confidence value for each metadata item. The confidence value represents the level of correctness and ambiguity of the textual information of the metadata item. The lower the ambiguity and the higher the prospective correctness, the higher the confidence value. The metadata items derived from the video metadata are analyzed in a specific order from high to low confidence level. Previously analyzed metadata are used as reference points in the context for subsequent disambiguation. The contextually most relevant entity is identified by means of descriptive texts and semantic relationships to the context. The context is created dynamically for each metadata item, taking into account the confidence value and other characteristics. The proposed semantic analysis follows two hypotheses: metadata items of a context should be processed in descendent order of their confidence value, and the metadata that pertains to a context should be limited by content-based segmentation boundaries. The evaluation results support the proposed hypotheses and show increased recall and precision for annotated entities, especially for metadata that originates from sources with low reliability. The algorithms have been evaluated against several state-of-the-art annotation approaches. The presented semantic analysis process is integrated into a video analysis framework and has been successfully applied in several projects for the purpose of semantic video exploration of videos. KW - Semantische Analyse KW - Kontext KW - Videoanalyse KW - Disambiguierung KW - Videometadaten KW - semantic analysis KW - context awareness KW - video analysis KW - word sense disambiguation KW - video metadata Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-70551 ER - TY - GEN A1 - Stojanovic, Vladeta A1 - Trapp, Matthias A1 - Richter, Rico A1 - Döllner, Jürgen Roland Friedrich T1 - A service-oriented approach for classifying 3D points clouds by example of office furniture classification T2 - Web3D 2018: Proceedings of the 23rd International ACM Conference on 3D Web Technology N2 - The rapid digitalization of the Facility Management (FM) sector has increased the demand for mobile, interactive analytics approaches concerning the operational state of a building. These approaches provide the key to increasing stakeholder engagement associated with Operation and Maintenance (O&M) procedures of living and working areas, buildings, and other built environment spaces. We present a generic and fast approach to process and analyze given 3D point clouds of typical indoor office spaces to create corresponding up-to-date approximations of classified segments and object-based 3D models that can be used to analyze, record and highlight changes of spatial configurations. The approach is based on machine-learning methods used to classify the scanned 3D point cloud data using 2D images. This approach can be used to primarily track changes of objects over time for comparison, allowing for routine classification, and presentation of results used for decision making. We specifically focus on classification, segmentation, and reconstruction of multiple different object types in a 3D point-cloud scene. We present our current research and describe the implementation of these technologies as a web-based application using a services-oriented methodology. KW - Indoor Models KW - 3D Point Clouds KW - Machine KW - Learning KW - BIM KW - Service-Oriented Y1 - 2018 SN - 978-1-4503-5800-2 U6 - https://doi.org/10.1145/3208806.3208810 SP - 1 EP - 9 PB - Association for Computing Machinery CY - New York ER - TY - GEN A1 - Sukmana, Muhammad Ihsan Haikal A1 - Torkura, Kennedy A. A1 - Graupner, Hendrik A1 - Cheng, Feng A1 - Meinel, Christoph T1 - Unified Cloud Access Control Model for Cloud Storage Broker T2 - 33rd International Conference on Information Networking (ICOIN 2019) N2 - Cloud Storage Broker (CSB) provides value-added cloud storage service for enterprise usage by leveraging multi-cloud storage architecture. However, it raises several challenges for managing resources and its access control in multiple Cloud Service Providers (CSPs) for authorized CSB stakeholders. In this paper we propose unified cloud access control model that provides the abstraction of CSP's services for centralized and automated cloud resource and access control management in multiple CSPs. Our proposal offers role-based access control for CSB stakeholders to access cloud resources by assigning necessary privileges and access control list for cloud resources and CSB stakeholders, respectively, following privilege separation concept and least privilege principle. We implement our unified model in a CSB system called CloudRAID for Business (CfB) with the evaluation result shows it provides system-and-cloud level security service for cfB and centralized resource and access control management in multiple CSPs. KW - Cloud Storage Broker KW - Cloud access control and resource management KW - Unified cloud model KW - Privilege separation concept KW - Least privilege principle KW - Role-based access control Y1 - 2019 SN - 978-1-5386-8350-7 U6 - https://doi.org/10.1109/ICOIN.2019.8717982 SN - 1976-7684 SP - 60 EP - 65 PB - IEEE CY - Los Alamitos ER - TY - CHAP A1 - Surajbali, Bholanathsingh A1 - Grace, Paul A1 - Coulson, Geoff T1 - Preserving dynamic reconfiguration consistency in aspect oriented middleware N2 - Aspect-oriented middleware is a promising technology for the realisation of dynamic reconfiguration in heterogeneous distributed systems. However, like other dynamic reconfiguration approaches, AO-middleware-based reconfiguration requires that the consistency of the system is maintained across reconfigurations. AO-middleware-based reconfiguration is an ongoing research topic and several consistency approaches have been proposed. However, most of these approaches tend to be targeted at specific contexts, whereas for distributed systems it is crucial to cover a wide range of operating conditions. In this paper we propose an approach that offers distributed, dynamic reconfiguration in a consistent manner, and features a flexible framework-based consistency management approach to cover a wide range of operating conditions. We evaluate our approach by investigating the configurability and transparency of our approach and also quantify the performance overheads of the associated consistency mechanisms. KW - middleware KW - reflection KW - aspects KW - dynamic reconfiguration KW - consistency Y1 - 2010 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-41379 ER - TY - THES A1 - Takouna, Ibrahim T1 - Energy-efficient and performance-aware virtual machine management for cloud data centers T1 - Energieeffizientes und performancebewusstes Management virtueller Maschinen für Cloud Datenzentren N2 - Virtualisierte Cloud Datenzentren stellen nach Bedarf Ressourcen zur Verfügu-ng, ermöglichen agile Ressourcenbereitstellung und beherbergen heterogene Applikationen mit verschiedenen Anforderungen an Ressourcen. Solche Datenzentren verbrauchen enorme Mengen an Energie, was die Erhöhung der Betriebskosten, der Wärme innerhalb der Zentren und des Kohlendioxidausstoßes verursacht. Der Anstieg des Energieverbrauches kann durch ein ineffektives Ressourcenmanagement, das die ineffiziente Ressourcenausnutzung verursacht, entstehen. Die vorliegende Dissertation stellt detaillierte Modelle und neue Verfahren für virtualisiertes Ressourcenmanagement in Cloud Datenzentren vor. Die vorgestellten Verfahren ziehen das Service-Level-Agreement (SLA) und die Heterogenität der Auslastung bezüglich des Bedarfs an Speicherzugriffen und Kommunikationsmustern von Web- und HPC- (High Performance Computing) Applikationen in Betracht. Um die präsentierten Techniken zu evaluieren, verwenden wir Simulationen und echte Protokollierung der Auslastungen von Web- und HPC- Applikationen. Außerdem vergleichen wir unser Techniken und Verfahren mit anderen aktuellen Verfahren durch die Anwendung von verschiedenen Performance Metriken. Die Hauptbeiträge dieser Dissertation sind Folgendes: Ein Proaktives auf robuster Optimierung basierendes Ressourcenbereitstellungsverfahren. Dieses Verfahren erhöht die Fähigkeit der Hostes zur Verfüg-ungsstellung von mehr VMs. Gleichzeitig aber wird der unnötige Energieverbrauch minimiert. Zusätzlich mindert diese Technik unerwünschte Ände-rungen im Energiezustand des Servers. Die vorgestellte Technik nutzt einen auf Intervall basierenden Vorhersagealgorithmus zur Implementierung einer robusten Optimierung. Dabei werden unsichere Anforderungen in Betracht gezogen. Ein adaptives und auf Intervall basierendes Verfahren zur Vorhersage des Arbeitsaufkommens mit hohen, in kürzer Zeit auftretenden Schwankungen. Die Intervall basierende Vorhersage ist implementiert in der Standard Abweichung Variante und in der Median absoluter Abweichung Variante. Die Intervall-Änderungen basieren auf einem adaptiven Vertrauensfenster um die Schwankungen des Arbeitsaufkommens zu bewältigen. Eine robuste VM Zusammenlegung für ein effizientes Energie und Performance Management. Dies ermöglicht die gegenseitige Abhängigkeit zwischen der Energie und der Performance zu minimieren. Unser Verfahren reduziert die Anzahl der VM-Migrationen im Vergleich mit den neu vor kurzem vorgestellten Verfahren. Dies trägt auch zur Reduzierung des durch das Netzwerk verursachten Energieverbrauches. Außerdem reduziert dieses Verfahren SLA-Verletzungen und die Anzahl von Änderungen an Energiezus-tänden. Ein generisches Modell für das Netzwerk eines Datenzentrums um die verzö-gerte Kommunikation und ihre Auswirkung auf die VM Performance und auf die Netzwerkenergie zu simulieren. Außerdem wird ein generisches Modell für ein Memory-Bus des Servers vorgestellt. Dieses Modell beinhaltet auch Modelle für die Latenzzeit und den Energieverbrauch für verschiedene Memory Frequenzen. Dies erlaubt eine Simulation der Memory Verzögerung und ihre Auswirkung auf die VM-Performance und auf den Memory Energieverbrauch. Kommunikation bewusste und Energie effiziente Zusammenlegung für parallele Applikationen um die dynamische Entdeckung von Kommunikationsmustern und das Umplanen von VMs zu ermöglichen. Das Umplanen von VMs benutzt eine auf den entdeckten Kommunikationsmustern basierende Migration. Eine neue Technik zur Entdeckung von dynamischen Mustern ist implementiert. Sie basiert auf der Signal Verarbeitung des Netzwerks von VMs, anstatt die Informationen des virtuellen Umstellung der Hosts oder der Initiierung der VMs zu nutzen. Das Ergebnis zeigt, dass unsere Methode die durchschnittliche Anwendung des Netzwerks reduziert und aufgrund der Reduzierung der aktiven Umstellungen Energie gespart. Außerdem bietet sie eine bessere VM Performance im Vergleich zu der CPU-basierten Platzierung. Memory bewusste VM Zusammenlegung für unabhängige VMs. Sie nutzt die Vielfalt des VMs Memory Zuganges um die Anwendung vom Memory-Bus der Hosts zu balancieren. Die vorgestellte Technik, Memory-Bus Load Balancing (MLB), verteilt die VMs reaktiv neu im Bezug auf ihre Anwendung vom Memory-Bus. Sie nutzt die VM Migration um die Performance des gesamtem Systems zu verbessern. Außerdem sind die dynamische Spannung, die Frequenz Skalierung des Memory und die MLB Methode kombiniert um ein besseres Energiesparen zu leisten. N2 - Virtualized cloud data centers provide on-demand resources, enable agile resource provisioning, and host heterogeneous applications with different resource requirements. These data centers consume enormous amounts of energy, increasing operational expenses, inducing high thermal inside data centers, and raising carbon dioxide emissions. The increase in energy consumption can result from ineffective resource management that causes inefficient resource utilization. This dissertation presents detailed models and novel techniques and algorithms for virtual resource management in cloud data centers. The proposed techniques take into account Service Level Agreements (SLAs) and workload heterogeneity in terms of memory access demand and communication patterns of web applications and High Performance Computing (HPC) applications. To evaluate our proposed techniques, we use simulation and real workload traces of web applications and HPC applications and compare our techniques against the other recently proposed techniques using several performance metrics. The major contributions of this dissertation are the following: proactive resource provisioning technique based on robust optimization to increase the hosts' availability for hosting new VMs while minimizing the idle energy consumption. Additionally, this technique mitigates undesirable changes in the power state of the hosts by which the hosts' reliability can be enhanced in avoiding failure during a power state change. The proposed technique exploits the range-based prediction algorithm for implementing robust optimization, taking into consideration the uncertainty of demand. An adaptive range-based prediction for predicting workload with high fluctuations in the short-term. The range prediction is implemented in two ways: standard deviation and median absolute deviation. The range is changed based on an adaptive confidence window to cope with the workload fluctuations. A robust VM consolidation for efficient energy and performance management to achieve equilibrium between energy and performance trade-offs. Our technique reduces the number of VM migrations compared to recently proposed techniques. This also contributes to a reduction in energy consumption by the network infrastructure. Additionally, our technique reduces SLA violations and the number of power state changes. A generic model for the network of a data center to simulate the communication delay and its impact on VM performance, as well as network energy consumption. In addition, a generic model for a memory-bus of a server, including latency and energy consumption models for different memory frequencies. This allows simulating the memory delay and its influence on VM performance, as well as memory energy consumption. Communication-aware and energy-efficient consolidation for parallel applications to enable the dynamic discovery of communication patterns and reschedule VMs using migration based on the determined communication patterns. A novel dynamic pattern discovery technique is implemented, based on signal processing of network utilization of VMs instead of using the information from the hosts' virtual switches or initiation from VMs. The result shows that our proposed approach reduces the network's average utilization, achieves energy savings due to reducing the number of active switches, and provides better VM performance compared to CPU-based placement. Memory-aware VM consolidation for independent VMs, which exploits the diversity of VMs' memory access to balance memory-bus utilization of hosts. The proposed technique, Memory-bus Load Balancing (MLB), reactively redistributes VMs according to their utilization of a memory-bus using VM migration to improve the performance of the overall system. Furthermore, Dynamic Voltage and Frequency Scaling (DVFS) of the memory and the proposed MLB technique are combined to achieve better energy savings. KW - Energieeffizienz KW - Cloud Datenzentren KW - Ressourcenmanagement KW - dynamische Umsortierung KW - energy efficiency KW - cloud datacenter KW - resource management KW - dynamic consolidation Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-72399 ER - TY - JOUR A1 - Takouna, Ibrahim A1 - Sachs, Kai A1 - Meinel, Christoph T1 - Multiperiod robust optimization for proactive resource provisioning in virtualized data centers JF - The journal of supercomputing : an internat. journal of supercomputer design, analysis and use KW - Energy-aware KW - Virtualization KW - Resource management KW - Robust optimization KW - Prediction Y1 - 2014 U6 - https://doi.org/10.1007/s11227-014-1246-2 SN - 0920-8542 SN - 1573-0484 VL - 70 IS - 3 SP - 1514 EP - 1536 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Taleb, Aiham A1 - Rohrer, Csaba A1 - Bergner, Benjamin A1 - De Leon, Guilherme A1 - Rodrigues, Jonas Almeida A1 - Schwendicke, Falk A1 - Lippert, Christoph A1 - Krois, Joachim T1 - Self-supervised learning methods for label-efficient dental caries classification JF - Diagnostics : open access journal N2 - High annotation costs are a substantial bottleneck in applying deep learning architectures to clinically relevant use cases, substantiating the need for algorithms to learn from unlabeled data. In this work, we propose employing self-supervised methods. To that end, we trained with three self-supervised algorithms on a large corpus of unlabeled dental images, which contained 38K bitewing radiographs (BWRs). We then applied the learned neural network representations on tooth-level dental caries classification, for which we utilized labels extracted from electronic health records (EHRs). Finally, a holdout test-set was established, which consisted of 343 BWRs and was annotated by three dental professionals and approved by a senior dentist. This test-set was used to evaluate the fine-tuned caries classification models. Our experimental results demonstrate the obtained gains by pretraining models using self-supervised algorithms. These include improved caries classification performance (6 p.p. increase in sensitivity) and, most importantly, improved label-efficiency. In other words, the resulting models can be fine-tuned using few labels (annotations). Our results show that using as few as 18 annotations can produce >= 45% sensitivity, which is comparable to human-level diagnostic performance. This study shows that self-supervision can provide gains in medical image analysis, particularly when obtaining labels is costly and expensive. KW - unsupervised methods KW - self-supervised learning KW - representation learning KW - dental caries classification KW - data driven approaches KW - annotation KW - efficient deep learning Y1 - 2022 U6 - https://doi.org/10.3390/diagnostics12051237 SN - 2075-4418 VL - 12 IS - 5 PB - MDPI CY - Basel ER - TY - GEN A1 - Tang, Mitchell A1 - Nakamoto, Carter H. A1 - Stern, Ariel Dora A1 - Mehrotra, Ateev T1 - Trends in remote patient monitoring use in traditional medicare T2 - JAMA internal medicine Y1 - 2022 U6 - https://doi.org/10.1001/jamainternmed.2022.3043 SN - 2168-6106 SN - 2168-6114 VL - 182 IS - 9 SP - 1005 EP - 1006 PB - American Medical Association CY - Chicago, Ill. ER - TY - BOOK A1 - Tessenow, Philipp A1 - Felgentreff, Tim A1 - Bracha, Gilad A1 - Hirschfeld, Robert T1 - Extending a dynamic programming language and runtime environment with access control T1 - Verbesserung gehosteter Dienste für kontinuierliche Integration N2 - Complexity in software systems is a major factor driving development and maintenance costs. To master this complexity, software is divided into modules that can be developed and tested separately. In order to support this separation of modules, each module should provide a clean and concise public interface. Therefore, the ability to selectively hide functionality using access control is an important feature in a programming language intended for complex software systems. Software systems are increasingly distributed, adding not only to their inherent complexity, but also presenting security challenges. The object-capability approach addresses these challenges by defining language properties providing only minimal capabilities to objects. One programming language that is based on the object-capability approach is Newspeak, a dynamic programming language designed for modularity and security. The Newspeak specification describes access control as one of Newspeak’s properties, because it is a requirement for the object-capability approach. However, access control, as defined in the Newspeak specification, is currently not enforced in its implementation. This work introduces an access control implementation for Newspeak, enabling the security of object-capabilities and enhancing modularity. We describe our implementation of access control for Newspeak. We adapted the runtime environment, the reflective system, the compiler toolchain, and the virtual machine. Finally, we describe a migration strategy for the existing Newspeak code base, so that our access control implementation can be integrated with minimal effort. N2 - Die Komplexität von Softwaresystemen hat einen hohen Einfluss auf Entwicklungs- und Wartungskosten. Um diese Komplexität zu beherschen, werden Softwaresysteme in Module unterteilt, da diese getrennt leichter zu entwickeln und zu testen sind. Zur Unterstützung einer sauberen Aufteilung von Modulen, sollten sie minimale und klar definierte Schnittstellen haben. Dafür ist die Fähigkeit, mit Hilfe der Berechtigungskontrolle selektiv die Sichtbarkeit von Funktionen eines Modules einzuschränken, von zentraler Bedeutung. Softwaresysteme sind immer stärker verteilt, was nicht nur zu ihrer Komplexität beiträgt, sondern auch Herausforderungen bezüglich der Sicherheit mit sich bringt. Der Object-Capability-Ansatz löst genau jene Sicherheitsprobleme, da dadurch Programmobjekten nur die minimal erforderlichen Fähigkeiten gegeben werden. Für diesen Ansatz ist es essentiell, dass die öffentliche Schnittstelle eines Objektes durch Berechtigungskontrolle eingeschränkt werden kann. Auf dem Object-Capability-Ansatz basiert Newspeak, eine moderne und dynamische Programmiersprache, die besonders auf Sicherheit sowie Modularität Wert legt. Die Berechtigungskontrolle ist eine zentrale Funktion, sowohl für die Modularität, als auch für die Sicherheit von Newspeak. Daher ist sie auch in der Spezifikation von Newspeak definiert. Bisher gibt es allerdings keine Implementierung, die die Berechtigungskontrolle durchsetzt. In dieser Arbeit stellen wir eine Implementierung der Berechtigungskontrolle für Newspeak vor. Damit wird sowohl die Modularität von Newspeak Programmen verbessert, als auch die Sicherheit durch den Object-Capability-Ansatz erst ermöglicht. Wir beschreiben eine Implementierung der Berechtigungskontrolle für Newspeak und passen dabei die Laufzeitumgebung, die Reflexions- und Introspektionsmodule, den Compiler sowie die virtuelle Maschine an. Große Teile des Newspeak-Programmcodes müssen für die Benutzung der Berechtigungskontrolle angepasst werden. Durch eine Migration des Newspeak-Programmcodes wird es möglich, unsere Implementierung mit existierenden Newspeak-Programmen zu benutzen. T3 - Technische Berichte des Hasso-Plattner-Instituts für Digital Engineering an der Universität Potsdam - 107 KW - access control KW - virtual machines KW - Newspeak KW - dynamic programming languages KW - Zugriffskontrolle KW - virtuelle Maschinen KW - Newspeak KW - dynamische Programmiersprachen Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-92560 SN - 978-3-86956-373-2 SN - 1613-5652 SN - 2191-1665 IS - 107 PB - Universitätsverlag Potsdam CY - Potsdam ER - TY - JOUR A1 - Thamsen, Lauritz A1 - Beilharz, Jossekin Jakob A1 - Vinh Thuy Tran, A1 - Nedelkoski, Sasho A1 - Kao, Odej T1 - Mary, Hugo, and Hugo* BT - learning to schedule distributed data-parallel processing jobs on shared clusters JF - Concurrency and computation : practice & experience N2 - Distributed data-parallel processing systems like MapReduce, Spark, and Flink are popular for analyzing large datasets using cluster resources. Resource management systems like YARN or Mesos in turn allow multiple data-parallel processing jobs to share cluster resources in temporary containers. Often, the containers do not isolate resource usage to achieve high degrees of overall resource utilization despite overprovisioning and the often fluctuating utilization of specific jobs. However, some combinations of jobs utilize resources better and interfere less with each other when running on the same shared nodes than others. This article presents an approach for improving the resource utilization and job throughput when scheduling recurring distributed data-parallel processing jobs in shared clusters. The approach is based on reinforcement learning and a measure of co-location goodness to have cluster schedulers learn over time which jobs are best executed together on shared resources. We evaluated this approach over the last years with three prototype schedulers that build on each other: Mary, Hugo, and Hugo*. For the evaluation we used exemplary Flink and Spark jobs from different application domains and clusters of commodity nodes managed by YARN. The results of these experiments show that our approach can increase resource utilization and job throughput significantly. KW - cluster resource management KW - distributed data-parallel processing KW - job KW - co-location KW - reinforcement learning KW - self-learning scheduler Y1 - 2020 U6 - https://doi.org/10.1002/cpe.5823 SN - 1532-0626 SN - 1532-0634 VL - 33 IS - 18 PB - Wiley CY - Hoboken ER - TY - THES A1 - Tinnefeld, Christian T1 - Building a columnar database on shared main memory-based storage BT - database operator placement in a shared main memory-based storage system that supports data access and code execution N2 - In the field of disk-based parallel database management systems exists a great variety of solutions based on a shared-storage or a shared-nothing architecture. In contrast, main memory-based parallel database management systems are dominated solely by the shared-nothing approach as it preserves the in-memory performance advantage by processing data locally on each server. We argue that this unilateral development is going to cease due to the combination of the following three trends: a) Nowadays network technology features remote direct memory access (RDMA) and narrows the performance gap between accessing main memory inside a server and of a remote server to and even below a single order of magnitude. b) Modern storage systems scale gracefully, are elastic, and provide high-availability. c) A modern storage system such as Stanford's RAMCloud even keeps all data resident in main memory. Exploiting these characteristics in the context of a main-memory parallel database management system is desirable. The advent of RDMA-enabled network technology makes the creation of a parallel main memory DBMS based on a shared-storage approach feasible. This thesis describes building a columnar database on shared main memory-based storage. The thesis discusses the resulting architecture (Part I), the implications on query processing (Part II), and presents an evaluation of the resulting solution in terms of performance, high-availability, and elasticity (Part III). In our architecture, we use Stanford's RAMCloud as shared-storage, and the self-designed and developed in-memory AnalyticsDB as relational query processor on top. AnalyticsDB encapsulates data access and operator execution via an interface which allows seamless switching between local and remote main memory, while RAMCloud provides not only storage capacity, but also processing power. Combining both aspects allows pushing-down the execution of database operators into the storage system. We describe how the columnar data processed by AnalyticsDB is mapped to RAMCloud's key-value data model and how the performance advantages of columnar data storage can be preserved. The combination of fast network technology and the possibility to execute database operators in the storage system opens the discussion for site selection. We construct a system model that allows the estimation of operator execution costs in terms of network transfer, data processed in memory, and wall time. This can be used for database operators that work on one relation at a time - such as a scan or materialize operation - to discuss the site selection problem (data pull vs. operator push). Since a database query translates to the execution of several database operators, it is possible that the optimal site selection varies per operator. For the execution of a database operator that works on two (or more) relations at a time, such as a join, the system model is enriched by additional factors such as the chosen algorithm (e.g. Grace- vs. Distributed Block Nested Loop Join vs. Cyclo-Join), the data partitioning of the respective relations, and their overlapping as well as the allowed resource allocation. We present an evaluation on a cluster with 60 nodes where all nodes are connected via RDMA-enabled network equipment. We show that query processing performance is about 2.4x slower if everything is done via the data pull operator execution strategy (i.e. RAMCloud is being used only for data access) and about 27% slower if operator execution is also supported inside RAMCloud (in comparison to operating only on main memory inside a server without any network communication at all). The fast-crash recovery feature of RAMCloud can be leveraged to provide high-availability, e.g. a server crash during query execution only delays the query response for about one second. Our solution is elastic in a way that it can adapt to changing workloads a) within seconds, b) without interruption of the ongoing query processing, and c) without manual intervention. N2 - Diese Arbeit beschreibt die Erstellung einer spalten-orientierten Datenbank auf einem geteilten, Hauptspeicher-basierenden Speichersystem. Motiviert wird diese Arbeit durch drei Faktoren. Erstens ist moderne Netzwerktechnologie mit “Remote Direct Memory Access” (RDMA) ausgestattet. Dies reduziert den Unterschied hinsichtlich Latenz und Durchsatz zwischen dem Speicherzugriff innerhalb eines Rechners und auf einen entfernten Rechner auf eine Größenordnung. Zweitens skalieren moderne Speichersysteme, sind elastisch und hochverfügbar. Drittens hält ein modernes Speichersystem wie Stanford's RAMCloud alle Daten im Hauptspeicher vor. Diese Eigenschaften im Kontext einer spalten-orientierten Datenbank zu nutzen ist erstrebenswert. Die Arbeit ist in drei Teile untergliedert. Der erste Teile beschreibt die Architektur einer spalten-orientierten Datenbank auf einem geteilten, Hauptspeicher-basierenden Speichersystem. Hierbei werden die im Rahmen dieser Arbeit entworfene und entwickelte Datenbank AnalyticsDB sowie Stanford's RAMCloud verwendet. Die Architektur beschreibt wie Datenzugriff und Operatorausführung gekapselt werden um nahtlos zwischen lokalem und entfernten Hauptspeicher wechseln zu können. Weiterhin wird die Ablage der nach einem relationalen Schema formatierten Daten von AnalyticsDB in RAMCloud behandelt, welches mit einem Schlüssel-Wertpaar Datenmodell operiert. Der zweite Teil fokussiert auf die Implikationen bei der Abarbeitung von Datenbankanfragen. Hier steht die Diskussion im Vordergrund wo (entweder in AnalyticsDB oder in RAMCloud) und mit welcher Parametrisierung einzelne Datenbankoperationen ausgeführt werden. Dafür werden passende Kostenmodelle vorgestellt, welche die Abbildung von Datenbankoperationen ermöglichen, die auf einer oder mehreren Relationen arbeiten. Der dritte Teil der Arbeit präsentiert eine Evaluierung auf einem Verbund von 60 Rechnern hinsichtlich der Leistungsfähigkeit, der Hochverfügbarkeit und der Elastizität vom System. T2 - Die Erstellung einer spaltenorientierten Datenbank auf einem verteilten, Hauptspeicher-basierenden Speichersystem KW - computer science KW - database technology KW - main memory computing KW - cloud computing KW - verteilte Datenbanken KW - Hauptspeicher Technologie KW - virtualisierte IT-Infrastruktur Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-72063 ER - TY - JOUR A1 - Torkura, Kennedy A. A1 - Sukmana, Muhammad Ihsan Haikal A1 - Cheng, Feng A1 - Meinel, Christoph T1 - CloudStrike BT - chaos engineering for security and resiliency in cloud infrastructure JF - IEEE access : practical research, open solutions N2 - Most cyber-attacks and data breaches in cloud infrastructure are due to human errors and misconfiguration vulnerabilities. Cloud customer-centric tools are imperative for mitigating these issues, however existing cloud security models are largely unable to tackle these security challenges. Therefore, novel security mechanisms are imperative, we propose Risk-driven Fault Injection (RDFI) techniques to address these challenges. RDFI applies the principles of chaos engineering to cloud security and leverages feedback loops to execute, monitor, analyze and plan security fault injection campaigns, based on a knowledge-base. The knowledge-base consists of fault models designed from secure baselines, cloud security best practices and observations derived during iterative fault injection campaigns. These observations are helpful for identifying vulnerabilities while verifying the correctness of security attributes (integrity, confidentiality and availability). Furthermore, RDFI proactively supports risk analysis and security hardening efforts by sharing security information with security mechanisms. We have designed and implemented the RDFI strategies including various chaos engineering algorithms as a software tool: CloudStrike. Several evaluations have been conducted with CloudStrike against infrastructure deployed on two major public cloud infrastructure: Amazon Web Services and Google Cloud Platform. The time performance linearly increases, proportional to increasing attack rates. Also, the analysis of vulnerabilities detected via security fault injection has been used to harden the security of cloud resources to demonstrate the effectiveness of the security information provided by CloudStrike. Therefore, we opine that our approaches are suitable for overcoming contemporary cloud security issues. KW - cloud security KW - security chaos engineering KW - resilient architectures KW - security risk assessment Y1 - 2020 U6 - https://doi.org/10.1109/ACCESS.2020.3007338 SN - 2169-3536 VL - 8 SP - 123044 EP - 123060 PB - Institute of Electrical and Electronics Engineers  CY - Piscataway ER - TY - GEN A1 - Torkura, Kennedy A. A1 - Sukmana, Muhammad Ihsan Haikal A1 - Cheng, Feng A1 - Meinel, Christoph T1 - Leveraging cloud native design patterns for security-as-a-service applications T2 - IEEE International Conference on Smart Cloud (SmartCloud) N2 - This paper discusses a new approach for designing and deploying Security-as-a-Service (SecaaS) applications using cloud native design patterns. Current SecaaS approaches do not efficiently handle the increasing threats to computer systems and applications. For example, requests for security assessments drastically increase after a high-risk security vulnerability is disclosed. In such scenarios, SecaaS applications are unable to dynamically scale to serve requests. A root cause of this challenge is employment of architectures not specifically fitted to cloud environments. Cloud native design patterns resolve this challenge by enabling certain properties e.g. massive scalability and resiliency via the combination of microservice patterns and cloud-focused design patterns. However adopting these patterns is a complex process, during which several security issues are introduced. In this work, we investigate these security issues, we redesign and deploy a monolithic SecaaS application using cloud native design patterns while considering appropriate, layered security counter-measures i.e. at the application and cloud networking layer. Our prototype implementation out-performs traditional, monolithic applications with an average Scanner Time of 6 minutes, without compromising security. Our approach can be employed for designing secure, scalable and performant SecaaS applications that effectively handle unexpected increase in security assessment requests. KW - Cloud-Security KW - Security-as-a-Service KW - Vulnerability Assessment KW - Cloud Native Applications Y1 - 2017 SN - 978-1-5386-3684-8 U6 - https://doi.org/10.1109/SmartCloud.2017.21 SP - 90 EP - 97 PB - Institute of Electrical and Electronics Engineers CY - New York ER - TY - THES A1 - Trapp, Matthias T1 - Interactive rendering techniques for focus+context visualization of 3D geovirtual environments T1 - Interaktive Rendering-Techniken für die Fokus-&-Kontext-Visualisierung von geovirtuellen 3D-Umgebungen N2 - This thesis introduces a collection of new real-time rendering techniques and applications for focus+context visualization of interactive 3D geovirtual environments such as virtual 3D city and landscape models. These environments are generally characterized by a large number of objects and are of high complexity with respect to geometry and textures. For these reasons, their interactive 3D rendering represents a major challenge. Their 3D depiction implies a number of weaknesses such as occlusions, cluttered image contents, and partial screen-space usage. To overcome these limitations and, thus, to facilitate the effective communication of geo-information, principles of focus+context visualization can be used for the design of real-time 3D rendering techniques for 3D geovirtual environments (see Figure). In general, detailed views of a 3D geovirtual environment are combined seamlessly with abstracted views of the context within a single image. To perform the real-time image synthesis required for interactive visualization, dedicated parallel processors (GPUs) for rasterization of computer graphics primitives are used. For this purpose, the design and implementation of appropriate data structures and rendering pipelines are necessary. The contribution of this work comprises the following five real-time rendering methods: • The rendering technique for 3D generalization lenses enables the combination of different 3D city geometries (e.g., generalized versions of a 3D city model) in a single image in real time. The method is based on a generalized and fragment-precise clipping approach, which uses a compressible, raster-based data structure. It enables the combination of detailed views in the focus area with the representation of abstracted variants in the context area. • The rendering technique for the interactive visualization of dynamic raster data in 3D geovirtual environments facilitates the rendering of 2D surface lenses. It enables a flexible combination of different raster layers (e.g., aerial images or videos) using projective texturing for decoupling image and geometry data. Thus, various overlapping and nested 2D surface lenses of different contents can be visualized interactively. • The interactive rendering technique for image-based deformation of 3D geovirtual environments enables the real-time image synthesis of non-planar projections, such as cylindrical and spherical projections, as well as multi-focal 3D fisheye-lenses and the combination of planar and non-planar projections. • The rendering technique for view-dependent multi-perspective views of 3D geovirtual environments, based on the application of global deformations to the 3D scene geometry, can be used for synthesizing interactive panorama maps to combine detailed views close to the camera (focus) with abstract views in the background (context). This approach reduces occlusions, increases the usage the available screen space, and reduces the overload of image contents. • The object-based and image-based rendering techniques for highlighting objects and focus areas inside and outside the view frustum facilitate preattentive perception. The concepts and implementations of interactive image synthesis for focus+context visualization and their selected applications enable a more effective communication of spatial information, and provide building blocks for design and development of new applications and systems in the field of 3D geovirtual environments. N2 - Die Darstellung immer komplexerer raumbezogener Information durch Geovisualisierung stellt die existierenden Technologien und den Menschen ständig vor neue Herausforderungen. In dieser Arbeit werden fünf neue, echtzeitfähige Renderingverfahren und darauf basierende Anwendungen für die Fokus-&-Kontext-Visualisierung von interaktiven geovirtuellen 3D-Umgebungen – wie virtuelle 3D-Stadt- und Landschaftsmodelle – vorgestellt. Die große Menge verschiedener darzustellender raumbezogener Information in 3D-Umgebungen führt oft zu einer hohen Anzahl unterschiedlicher Objekte und somit zu einer hohen Geometrie- und Texturkomplexität. In der Folge verlieren 3D-Darstellungen durch Verdeckungen, überladene Bildinhalte und eine geringe Ausnutzung des zur Verfügung stehenden Bildraumes an Informationswert. Um diese Beschränkungen zu kompensieren und somit die Kommunikation raumbezogener Information zu verbessern, kann das Prinzip der Fokus-&-Kontext-Visualisierung angewendet werden. Hierbei wird die für den Nutzer wesentliche Information als detaillierte Ansicht im Fokus mit abstrahierter Kontextinformation nahtlos miteinander kombiniert. Um das für die interaktive Visualisierung notwendige Echtzeit-Rendering durchzuführen, können spezialisierte Parallelprozessoren für die Rasterisierung von computergraphischen Primitiven (GPUs) verwendet werden. Dazu ist die Konzeption und Implementierung von geeigneten Datenstrukturen und Rendering-Pipelines notwendig. Der Beitrag dieser Arbeit umfasst die folgenden fünf Renderingverfahren. • Das Renderingverfahren für interaktive 3D-Generalisierungslinsen: Hierbei wird die Kombination unterschiedlicher 3D-Szenengeometrien, z. B. generalisierte Varianten eines 3DStadtmodells, in einem Bild ermöglicht. Das Verfahren basiert auf einem generalisierten Clipping-Ansatz, der es erlaubt, unter Verwendung einer komprimierbaren, rasterbasierten Datenstruktur beliebige Bereiche einer 3D-Szene freizustellen bzw. zu kappen. Somit lässt sich eine Kombination von detaillierten Ansichten im Fokusbereich mit der Darstellung einer abstrahierten Variante im Kontextbereich implementieren. • Das Renderingverfahren zur Visualisierung von dynamischen Raster-Daten in geovirtuellen 3D-Umgebungen zur Darstellung von 2D-Oberflächenlinsen: Die Verwendung von projektiven Texturen zur Entkoppelung von Bild- und Geometriedaten ermöglicht eine flexible Kombination verschiedener Rasterebenen (z.B. Luftbilder oder Videos). Somit können verschiedene überlappende sowie verschachtelte 2D-Oberflächenlinsen mit unterschiedlichen Dateninhalten interaktiv visualisiert werden. • Das Renderingverfahren zur bildbasierten Deformation von geovirtuellen 3D-Umgebungen: Neben der interaktiven Bildsynthese von nicht-planaren Projektionen, wie beispielsweise zylindrischen oder sphärischen Panoramen, lassen sich mit diesem Verfahren multifokale 3D-Fischaugen-Linsen erzeugen sowie planare und nicht-planare Projektionen miteinander kombinieren. • Das Renderingverfahren für die Generierung von sichtabhängigen multiperspektivischen Ansichten von geovirtuellen 3D-Umgebungen: Das Verfahren basiert auf globalen Deformationen der 3D-Szenengeometrie und kann zur Erstellung von interaktiven 3D-Panoramakarten verwendet werden, welche beispielsweise detaillierte Absichten nahe der virtuellen Kamera (Fokus) mit abstrakten Ansichten im Hintergrund (Kontext) kombinieren. Dieser Ansatz reduziert Verdeckungen, nutzt den zur Verfügung stehenden Bildraum in verbesserter Weise aus und reduziert das Überladen von Bildinhalten. • Objekt-und bildbasierte Renderingverfahren für die Hervorhebung von Fokus-Objekten und Fokus-Bereichen innerhalb und außerhalb des sichtbaren Bildausschnitts, um die präattentive Wahrnehmung eines Benutzers besser zu unterstützen. Die in dieser Arbeit vorgestellten Konzepte, Entwürfe und Implementierungen von interaktiven Renderingverfahren zur Fokus-&-Kontext-Visualisierung sowie deren ausgewählte Anwendungen ermöglichen eine effektivere Kommunikation raumbezogener Information und repräsentieren softwaretechnische Bausteine für die Entwicklung neuer Anwendungen und Systeme im Bereich der geovirtuellen 3D-Umgebungen. KW - 3D Computer Grafik KW - Interaktives Rendering KW - Fokus-&-Kontext Visualisierung KW - 3D Computer Graphics KW - Interactive Rendering KW - Focus+Context Visualization Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-66824 ER - TY - GEN A1 - Trapp, Matthias A1 - Döllner, Jürgen Roland Friedrich ED - Banissi, E Ursyn T1 - Interactive Close-Up Rendering for Detail plus Overview Visualization of 3D Digital Terrain Models T2 - 2019 23rd International Conference Information Visualisation (IV) N2 - This paper presents an interactive rendering technique for detail+overview visualization of 3D digital terrain models using interactive close-ups. A close-up is an alternative presentation of input data varying with respect to geometrical scale, mapping, appearance, as well as Level-of-Detail (LOD) and Level-of-Abstraction (LOA) used. The presented 3D close-up approach enables in-situ comparison of multiple Regionof-Interests (ROIs) simultaneously. We describe a GPU-based rendering technique for the image-synthesis of multiple close-ups in real-time. KW - Terrain Visualization KW - Detail plus Overview KW - Close-Up KW - Coordinated and Multiple Views Y1 - 2019 SN - 978-1-7281-2838-2 SN - 978-1-7281-2839-9 U6 - https://doi.org/10.1109/IV.2019.00053 SN - 2375-0138 SN - 1550-6037 SP - 275 EP - 280 PB - Inst. of Electr. and Electronics Engineers CY - Los Alamitos ER - TY - GEN A1 - Trapp, Matthias A1 - Döllner, Jürgen Roland Friedrich T1 - Real-time Screen-space Geometry Draping for 3D Digital Terrain Models T2 - 2019 23rd International Conference Information Visualisation (IV) N2 - A fundamental task in 3D geovisualization and GIS applications is the visualization of vector data that can represent features such as transportation networks or land use coverage. Mapping or draping vector data represented by geometric primitives (e.g., polylines or polygons) to 3D digital elevation or 3D digital terrain models is a challenging task. We present an interactive GPU-based approach that performs geometry-based draping of vector data on per-frame basis using an image-based representation of a 3D digital elevation or terrain model only. KW - Geometry Draping KW - Geovisualization KW - GPU-based Real-time Rendering Y1 - 2019 SN - 978-1-7281-2838-2 SN - 978-1-7281-2839-9 U6 - https://doi.org/10.1109/IV.2019.00054 SN - 2375-0138 SN - 1550-6037 SP - 281 EP - 286 PB - Inst. of Electr. and Electronics Engineers CY - Los Alamitos ER - TY - JOUR A1 - Troeger, Peter A1 - Polze, Andreas T1 - Object and process migration in .NET N2 - Many of today's distributed computing systems in the field do not Support the migration of execution entities among computing nodes (luring runtime. The relatively static association between units of processing and computing nodes makes it difficult to implement fault-tolerant behavior or load-balancing schemes. The concept of code migration may provide a solution to the above-mentioned problems. it can be defined as the movement of processes, objects, or components from one computing node to another during system runtime in a distributed environment. With the advent of the virtual machine-based NET framework, many of the cross-language heterogeneity issues have been resolved. With the commercial implementation, the shared source "Rotor", and the open-source "Mono" implementation on hand, we have focused on cross-operating system heterogeneity issues and present interoperability and migration schemes for applications distributed over different operating systems (namely Linux and Windows 2000) as well as various NET implementations. Within this paper, we describe the integration of a migration facility with the hell) of Aspect- Oriented Programming (AOP) into the NET framework. AOP is interesting as it addresses non-functional system properties on the middleware level, without the need to manipulate lower system layers like the operating system itself. Most features required to implement object or process migration (such as reflection mechanisms or a machine-independent executable format) are already present in the NET frameworks, so the integration of such a concept is a natural extension of the system capabilities. We have implemented several proof-of-concept applications for different use case scenarios. The paper contains an experimental evaluation of the performance impact of object migration in context of those applications. Y1 - 2009 SN - 0267-6192 ER - TY - THES A1 - Trümper, Jonas T1 - Visualization techniques for the analysis of software behavior and related structures T1 - Visualisierungstechniken für die Analyse von Softwareverhalten und verwandter Strukturen N2 - Software maintenance encompasses any changes made to a software system after its initial deployment and is thereby one of the key phases in the typical software-engineering lifecycle. In software maintenance, we primarily need to understand structural and behavioral aspects, which are difficult to obtain, e.g., by code reading. Software analysis is therefore a vital tool for maintaining these systems: It provides - the preferably automated - means to extract and evaluate information from their artifacts such as software structure, runtime behavior, and related processes. However, such analysis typically results in massive raw data, so that even experienced engineers face difficulties directly examining, assessing, and understanding these data. Among other things, they require tools with which to explore the data if no clear question can be formulated beforehand. For this, software analysis and visualization provide its users with powerful interactive means. These enable the automation of tasks and, particularly, the acquisition of valuable and actionable insights into the raw data. For instance, one means for exploring runtime behavior is trace visualization. This thesis aims at extending and improving the tool set for visual software analysis by concentrating on several open challenges in the fields of dynamic and static analysis of software systems. This work develops a series of concepts and tools for the exploratory visualization of the respective data to support users in finding and retrieving information on the system artifacts concerned. This is a difficult task, due to the lack of appropriate visualization metaphors; in particular, the visualization of complex runtime behavior poses various questions and challenges of both a technical and conceptual nature. This work focuses on a set of visualization techniques for visually representing control-flow related aspects of software traces from shared-memory software systems: A trace-visualization concept based on icicle plots aids in understanding both single-threaded as well as multi-threaded runtime behavior on the function level. The concept’s extensibility further allows the visualization and analysis of specific aspects of multi-threading such as synchronization, the correlation of such traces with data from static software analysis, and a comparison between traces. Moreover, complementary techniques for simultaneously analyzing system structures and the evolution of related attributes are proposed. These aim at facilitating long-term planning of software architecture and supporting management decisions in software projects by extensions to the circular-bundle-view technique: An extension to 3-dimensional space allows for the use of additional variables simultaneously; interaction techniques allow for the modification of structures in a visual manner. The concepts and techniques presented here are generic and, as such, can be applied beyond software analysis for the visualization of similarly structured data. The techniques' practicability is demonstrated by several qualitative studies using subject data from industry-scale software systems. The studies provide initial evidence that the techniques' application yields useful insights into the subject data and its interrelationships in several scenarios. N2 - Die Softwarewartung umfasst alle Änderungen an einem Softwaresystem nach dessen initialer Bereitstellung und stellt damit eine der wesentlichen Phasen im typischen Softwarelebenszyklus dar. In der Softwarewartung müssen wir insbesondere strukturelle und verhaltensbezogene Aspekte verstehen, welche z.B. alleine durch Lesen von Quelltext schwer herzuleiten sind. Die Softwareanalyse ist daher ein unverzichtbares Werkzeug zur Wartung solcher Systeme: Sie bietet - vorzugsweise automatisierte - Mittel, um Informationen über deren Artefakte, wie Softwarestruktur, Laufzeitverhalten und verwandte Prozesse, zu extrahieren und zu evaluieren. Eine solche Analyse resultiert jedoch typischerweise in großen und größten Rohdaten, die selbst erfahrene Softwareingenieure direkt nur schwer untersuchen, bewerten und verstehen können. Unter Anderem dann, wenn vorab keine klare Frage formulierbar ist, benötigen sie Werkzeuge, um diese Daten zu erforschen. Hierfür bietet die Softwareanalyse und Visualisierung ihren Nutzern leistungsstarke, interaktive Mittel. Diese ermöglichen es Aufgaben zu automatisieren und insbesondere wertvolle und belastbare Einsichten aus den Rohdaten zu erlangen. Beispielsweise ist die Visualisierung von Software-Traces ein Mittel, um das Laufzeitverhalten eines Systems zu ergründen. Diese Arbeit zielt darauf ab, den "Werkzeugkasten" der visuellen Softwareanalyse zu erweitern und zu verbessern, indem sie sich auf bestimmte, offene Herausforderungen in den Bereichen der dynamischen und statischen Analyse von Softwaresystemen konzentriert. Die Arbeit entwickelt eine Reihe von Konzepten und Werkzeugen für die explorative Visualisierung der entsprechenden Daten, um Nutzer darin zu unterstützen, Informationen über betroffene Systemartefakte zu lokalisieren und zu verstehen. Da es insbesondere an geeigneten Visualisierungsmetaphern mangelt, ist dies eine schwierige Aufgabe. Es bestehen, insbesondere bei komplexen Softwaresystemen, verschiedenste offene technische sowie konzeptionelle Fragestellungen und Herausforderungen. Diese Arbeit konzentriert sich auf Techniken zur visuellen Darstellung kontrollflussbezogener Aspekte aus Software-Traces von Shared-Memory Softwaresystemen: Ein Trace-Visualisierungskonzept, basierend auf Icicle Plots, unterstützt das Verstehen von single- und multi-threaded Laufzeitverhalten auf Funktionsebene. Die Erweiterbarkeit des Konzepts ermöglicht es zudem spezifische Aspekte des Multi-Threading, wie Synchronisation, zu visualisieren und zu analysieren, derartige Traces mit Daten aus der statischen Softwareanalyse zu korrelieren sowie Traces mit einander zu vergleichen. Darüber hinaus werden komplementäre Techniken für die kombinierte Analyse von Systemstrukturen und der Evolution zugehöriger Eigenschaften vorgestellt. Diese zielen darauf ab, die Langzeitplanung von Softwarearchitekturen und Management-Entscheidungen in Softwareprojekten mittels Erweiterungen an der Circular-Bundle-View-Technik zu unterstützen: Eine Erweiterung auf den 3-dimensionalen Raum ermöglicht es zusätzliche visuelle Variablen zu nutzen; Strukturen können mithilfe von Interaktionstechniken visuell bearbeitet werden. Die gezeigten Techniken und Konzepte sind allgemein verwendbar und lassen sich daher auch jenseits der Softwareanalyse einsetzen, um ähnlich strukturierte Daten zu visualisieren. Mehrere qualitative Studien an Softwaresystemen in industriellem Maßstab stellen die Praktikabilität der Techniken dar. Die Ergebnisse sind erste Belege dafür, dass die Anwendung der Techniken in verschiedenen Szenarien nützliche Einsichten in die untersuchten Daten und deren Zusammenhänge liefert. KW - Visualisierung KW - Softwarewartung KW - Softwareanalyse KW - Softwarevisualisierung KW - Laufzeitverhalten KW - visualization KW - software maintenance KW - software analysis KW - software visualization KW - runtime behavior Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-72145 ER - TY - JOUR A1 - Vaid, Akhil A1 - Chan, Lili A1 - Chaudhary, Kumardeep A1 - Jaladanki, Suraj K. A1 - Paranjpe, Ishan A1 - Russak, Adam J. A1 - Kia, Arash A1 - Timsina, Prem A1 - Levin, Matthew A. A1 - He, John Cijiang A1 - Böttinger, Erwin A1 - Charney, Alexander W. A1 - Fayad, Zahi A. A1 - Coca, Steven G. A1 - Glicksberg, Benjamin S. A1 - Nadkarni, Girish N. T1 - Predictive approaches for acute dialysis requirement and death in COVID-19 JF - Clinical journal of the American Society of Nephrology : CJASN N2 - Background and objectives AKI treated with dialysis initiation is a common complication of coronavirus disease 2019 (COVID-19) among hospitalized patients. However, dialysis supplies and personnel are often limited. Design, setting, participants, & measurements Using data from adult patients hospitalized with COVID-19 from five hospitals from theMount Sinai Health System who were admitted between March 10 and December 26, 2020, we developed and validated several models (logistic regression, Least Absolute Shrinkage and Selection Operator (LASSO), random forest, and eXtreme GradientBoosting [XGBoost; with and without imputation]) for predicting treatment with dialysis or death at various time horizons (1, 3, 5, and 7 days) after hospital admission. Patients admitted to theMount Sinai Hospital were used for internal validation, whereas the other hospitals formed part of the external validation cohort. Features included demographics, comorbidities, and laboratory and vital signs within 12 hours of hospital admission. Results A total of 6093 patients (2442 in training and 3651 in external validation) were included in the final cohort. Of the different modeling approaches used, XGBoost without imputation had the highest area under the receiver operating characteristic (AUROC) curve on internal validation (range of 0.93-0.98) and area under the precisionrecall curve (AUPRC; range of 0.78-0.82) for all time points. XGBoost without imputation also had the highest test parameters on external validation (AUROC range of 0.85-0.87, and AUPRC range of 0.27-0.54) across all time windows. XGBoost without imputation outperformed all models with higher precision and recall (mean difference in AUROC of 0.04; mean difference in AUPRC of 0.15). Features of creatinine, BUN, and red cell distribution width were major drivers of the model's prediction. Conclusions An XGBoost model without imputation for prediction of a composite outcome of either death or dialysis in patients positive for COVID-19 had the best performance, as compared with standard and other machine learning models. KW - COVID-19 KW - dialysis KW - machine learning KW - prediction KW - AKI Y1 - 2021 U6 - https://doi.org/10.2215/CJN.17311120 SN - 1555-9041 SN - 1555-905X VL - 16 IS - 8 SP - 1158 EP - 1168 PB - American Society of Nephrology CY - Washington ER -