@phdthesis{Kluth2011,
  author    = {Kluth, Stephan},
  title     = {Quantitative modeling and analysis with FMC-QE},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-52987},
  school      = {Universit{\"a}t Potsdam},
  year      = {2011},
  abstract  = {The modeling and evaluation calculus FMC-QE, the Fundamental Modeling Concepts for Quanti-tative Evaluation [1], extends the Fundamental Modeling Concepts (FMC) for performance modeling and prediction. In this new methodology, the hierarchical service requests are in the main focus, because they are the origin of every service provisioning process. Similar to physics, these service requests are a tuple of value and unit, which enables hierarchical service request transformations at the hierarchical borders and therefore the hierarchical modeling. Through reducing the model complexity of the models by decomposing the system in different hierarchical views, the distinction between operational and control states and the calculation of the performance values on the assumption of the steady state, FMC-QE has a scalable applica-bility on complex systems. According to FMC, the system is modeled in a 3-dimensional hierarchical representation space, where system performance parameters are described in three arbitrarily fine-grained hierarchi-cal bipartite diagrams. The hierarchical service request structures are modeled in Entity Relationship Diagrams. The static server structures, divided into logical and real servers, are de-scribed as Block Diagrams. The dynamic behavior and the control structures are specified as Petri Nets, more precisely Colored Time Augmented Petri Nets. From the structures and pa-rameters of the performance model, a hierarchical set of equations is derived. The calculation of the performance values is done on the assumption of stationary processes and is based on fundamental laws of the performance analysis: Little's Law and the Forced Traffic Flow Law. Little's Law is used within the different hierarchical levels (horizontal) and the Forced Traffic Flow Law is the key to the dependencies among the hierarchical levels (vertical). This calculation is suitable for complex models and allows a fast (re-)calculation of different performance scenarios in order to support development and configuration decisions. Within the Research Group Zorn at the Hasso Plattner Institute, the work is embedded in a broader research in the development of FMC-QE. While this work is concentrated on the theoretical background, description and definition of the methodology as well as the extension and validation of the applicability, other topics are in the development of an FMC-QE modeling and evaluation tool and the usage of FMC-QE in the design of an adaptive transport layer in order to fulfill Quality of Service and Service Level Agreements in volatile service based environments. This thesis contains a state-of-the-art, the description of FMC-QE as well as extensions of FMC-QE in representative general models and case studies. In the state-of-the-art part of the thesis in chapter 2, an overview on existing Queueing Theory and Time Augmented Petri Net models and other quantitative modeling and evaluation languages and methodologies is given. Also other hierarchical quantitative modeling frameworks will be considered. The description of FMC-QE in chapter 3 consists of a summary of the foundations of FMC-QE, basic definitions, the graphical notations, the FMC-QE Calculus and the modeling of open queueing networks as an introductory example. The extensions of FMC-QE in chapter 4 consist of the integration of the summation method in order to support the handling of closed networks and the modeling of multiclass and semaphore scenarios. Furthermore, FMC-QE is compared to other performance modeling and evaluation approaches. In the case study part in chapter 5, proof-of-concept examples, like the modeling of a service based search portal, a service based SAP NetWeaver application and the Axis2 Web service framework will be provided. Finally, conclusions are given by a summary of contributions and an outlook on future work in chapter 6. [1] Werner Zorn. FMC-QE - A New Approach in Quantitative Modeling. In Hamid R. Arabnia, editor, Procee-dings of the International Conference on Modeling, Simulation and Visualization Methods (MSV 2007) within WorldComp '07, pages 280 - 287, Las Vegas, NV, USA, June 2007. CSREA Press. ISBN 1-60132-029-9.},
  language  = {en}
}
@phdthesis{Off2011,
  author    = {Off, Thomas},
  title     = {Durchg{\"a}ngige Verfolgbarkeit im Vorfeld der Softwareentwicklung von E-Government-Anwendungen : ein ontologiebasierter und modellgetriebener Ansatz am Beispiel von B{\"u}rgerdiensten},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-57478},
  school      = {Universit{\"a}t Potsdam},
  year      = {2011},
  abstract  = {Die {\"o}ffentliche Verwaltung setzt seit mehreren Jahren E-Government-Anwendungssysteme ein, um ihre Verwaltungsprozesse intensiver mit moderner Informationstechnik zu unterst{\"u}tzen. Da die {\"o}ffentliche Verwaltung in ihrem Handeln in besonderem Maße an Recht und Gesetz gebunden ist verst{\"a}rkt und verbreitet sich der Zusammenhang zwischen den Gesetzen und Rechtsvorschriften einerseits und der zur Aufgabenunterst{\"u}tzung eingesetzten Informationstechnik andererseits. Aus Sicht der Softwaretechnik handelt es sich bei diesem Zusammenhang um eine spezielle Form der Verfolgbarkeit von Anforderungen (engl. Traceability), die so genannte Verfolgbarkeit im Vorfeld der Anforderungsspezifikation (Pre-Requirements Specification Traceability, kurz Pre-RS Traceability), da sie Aspekte betrifft, die relevant sind, bevor die Anforderungen in eine Spezifikation eingeflossen sind (Urspr{\"u}nge von Anforderungen). Der Ansatz dieser Arbeit leistet einen Beitrag zur Verfolgbarkeit im Vorfeld der Anforderungsspezifikation von E-Government-Anwendungssystemen. Er kombiniert dazu aktuelle Entwicklungen und Standards (insbesondere des World Wide Web Consortium und der Object Management Group) aus den Bereichen Verfolgbarkeit von Anforderungen, Semantic Web, Ontologiesprachen und modellgetriebener Softwareentwicklung. Der L{\"o}sungsansatz umfasst eine spezielle Ontologie des Verwaltungshandeln, die mit den Techniken, Methoden und Werkzeugen des Semantic Web eingesetzt wird, um in Texten von Rechtsvorschriften relevante Urspr{\"u}nge von Anforderungen durch Annotationen mit einer definierten Semantik zu versehen. Darauf aufbauend wird das Ontology Definition Metamodel (ODM) verwendet, um die Annotationen als spezielle Individuen einer Ontologie auf Elemente der Unified Modeling Language (UML) abzubilden. Dadurch entsteht ein neuer Modelltyp Pre-Requirements Model (PRM), der das Vorfeld der Anforderungsspezifikation formalisiert. Modelle diesen Typs k{\"o}nnen auch verwendet werden, um Aspekte zu formalisieren die sich nicht oder nicht vollst{\"a}ndig aus dem Text der Rechtsvorschrift ergeben. Weiterhin bietet das Modell die M{\"o}glichkeit zum Anschluss an die modellgetriebene Softwareentwicklung. In der Arbeit wird deshalb eine Erweiterung der Model Driven Architecture (MDA) vorgeschlagen. Zus{\"a}tzlich zu den etablierten Modelltypen Computation Independent Model (CIM), Platform Independent Model (PIM) und Platform Specific Model (PSM) k{\"o}nnte der Einsatz des PRM Vorteile f{\"u}r die Verfolgbarkeit bringen. Wird die MDA mit dem PRM auf das Vorfeld der Anforderungsspezifikation ausgeweitet, kann eine Transformation des PRM in ein CIM als initiale Anforderungsspezifikation erfolgen, indem der MOF Query View Transformation Standard (QVT) eingesetzt wird. Als Teil des QVT-Standards ist die Aufzeichnung von Verfolgbarkeitsinformationen bei Modelltransformationen verbindlich. Um die semantische L{\"u}cke zwischen PRM und CIM zu {\"u}berbr{\"u}cken, erfolgt analog zum Einsatz des Plattformmodells (PM) in der PIM nach PSM Transformation der Einsatz spezieller Hilfsmodelle. Es kommen daf{\"u}r die im Projekt "E-LoGo" an der Universit{\"a}t Potsdam entwickelten Referenzmodelle zum Einsatz. Durch die Aufzeichnung der Abbildung annotierter Textelemente auf Elemente im PRM und der Transformation der Elemente des PRM in Elemente des CIM kann durchg{\"a}ngige Verfolgbarkeit im Vorfeld der Anforderungsspezifikation erreicht werden. Der Ansatz basiert auf einer so genannten Verfolgbarkeitsdokumentation in Form verlinkter Hypertextdokumente, die mittels XSL-Stylesheet erzeugt wurden und eine Verbindung zur graphischen Darstellung des Diagramms (z. B. Anwendungsfall-, Klassendiagramm der UML) haben. Der Ansatz unterst{\"u}tzt die horizontale Verfolgbarkeit zwischen Elementen unterschiedlicher Modelle vorw{\"a}rts- und r{\"u}ckw{\"a}rtsgerichtet umfassend. Er bietet außerdem vertikale Verfolgbarkeit, die Elemente des gleichen Modells und verschiedener Modellversionen in Beziehung setzt. {\"U}ber den offensichtlichen Nutzen einer durchg{\"a}ngigen Verfolgbarkeit im Vorfeld der Anforderungsspezifikation (z. B. Analyse der Auswirkungen einer Gesetzes{\"a}nderung, Ber{\"u}cksichtigung des vollst{\"a}ndigen Kontextes einer Anforderung bei ihrer Priorisierung) hinausgehend, bietet diese Arbeit eine erste Ansatzm{\"o}glichkeit f{\"u}r eine Feedback-Schleife im Prozess der Gesetzgebung. Stehen beispielsweise mehrere gleichwertige Gestaltungsoptionen eines Gesetzes zur Auswahl, k{\"o}nnen die Auswirkungen jeder Option analysiert und der Aufwand ihrer Umsetzung in E-Government-Anwendungen als Auswahlkriterium ber{\"u}cksichtigt werden. Die am 16. M{\"a}rz 2011 in Kraft getretene {\"A}nderung des NKRG schreibt eine solche Analyse des so genannten „Erf{\"u}llungsaufwands" f{\"u}r Teilbereiche des Verwaltungshandelns bereits heute verbindlich vor. F{\"u}r diese Analyse kann die vorliegende Arbeit einen Ansatz bieten, um zu fundierten Aussagen {\"u}ber den {\"A}nderungsaufwand eingesetzter E-Government-Anwendungssysteme zu kommen.},
  language  = {de}
}
@phdthesis{Berg2013,
  author    = {Berg, Gregor},
  title     = {Virtual prototypes for the model-based elicitation and validation of collaborative scenarios},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-69729},
  school      = {Universit{\"a}t Potsdam},
  year      = {2013},
  abstract  = {Requirements engineers have to elicit, document, and validate how stakeholders act and interact to achieve their common goals in collaborative scenarios. Only after gathering all information concerning who interacts with whom to do what and why, can a software system be designed and realized which supports the stakeholders to do their work. To capture and structure requirements of different (groups of) stakeholders, scenario-based approaches have been widely used and investigated. Still, the elicitation and validation of requirements covering collaborative scenarios remains complicated, since the required information is highly intertwined, fragmented, and distributed over several stakeholders. Hence, it can only be elicited and validated collaboratively. In times of globally distributed companies, scheduling and conducting workshops with groups of stakeholders is usually not feasible due to budget and time constraints. Talking to individual stakeholders, on the other hand, is feasible but leads to fragmented and incomplete stakeholder scenarios. Going back and forth between different individual stakeholders to resolve this fragmentation and explore uncovered alternatives is an error-prone, time-consuming, and expensive task for the requirements engineers. While formal modeling methods can be employed to automatically check and ensure consistency of stakeholder scenarios, such methods introduce additional overhead since their formal notations have to be explained in each interaction between stakeholders and requirements engineers. Tangible prototypes as they are used in other disciplines such as design, on the other hand, allow designers to feasibly validate and iterate concepts and requirements with stakeholders. This thesis proposes a model-based approach for prototyping formal behavioral specifications of stakeholders who are involved in collaborative scenarios. By simulating and animating such specifications in a remote domain-specific visualization, stakeholders can experience and validate the scenarios captured so far, i.e., how other stakeholders act and react. This interactive scenario simulation is referred to as a model-based virtual prototype. Moreover, through observing how stakeholders interact with a virtual prototype of their collaborative scenarios, formal behavioral specifications can be automatically derived which complete the otherwise fragmented scenarios. This, in turn, enables requirements engineers to elicit and validate collaborative scenarios in individual stakeholder sessions - decoupled, since stakeholders can participate remotely and are not forced to be available for a joint session at the same time. This thesis discusses and evaluates the feasibility, understandability, and modifiability of model-based virtual prototypes. Similarly to how physical prototypes are perceived, the presented approach brings behavioral models closer to being tangible for stakeholders and, moreover, combines the advantages of joint stakeholder sessions and decoupled sessions.},
  language  = {en}
}
@phdthesis{Koehlmann2016,
  author    = {K{\"o}hlmann, Wiebke},
  title     = {Zug{\"a}nglichkeit virtueller Klassenzimmer f{\"u}r Blinde},
  publisher = {Logos},
  address   = {Berlin},
  isbn      = {978-3-8325-4273-3},
  pages     = {i-x, 310, i-clxxvi},
  year      = {2016},
  abstract  = {E-Learning-Anwendungen bieten Chancen f{\"u}r die gesetzlich vorgeschriebene Inklusion von Lernenden mit Beeintr{\"a}chtigungen. Die gleichberechtigte Teilhabe von blinden Lernenden an Veranstaltungen in virtuellen Klassenzimmern ist jedoch durch den synchronen, multimedialen Charakter und den hohen Informationsumfang dieser L{\"o}sungen kaum m{\"o}glich. Die vorliegende Arbeit untersucht die Zug{\"a}nglichkeit virtueller Klassenzimmer f{\"u}r blinde Nutzende, um eine m{\"o}glichst gleichberechtigte Teilhabe an synchronen, kollaborativen Lernszenarien zu erm{\"o}glichen. Im Rahmen einer Produktanalyse werden dazu virtuelle Klassenzimmer auf ihre Zug{\"a}nglichkeit und bestehende Barrieren untersucht und Richtlinien f{\"u}r die zug{\"a}ngliche Gestaltung von virtuellen Klassenzimmern definiert. Anschließend wird ein alternatives Benutzungskonzept zur Darstellung und Bedienung virtueller Klassenzimmer auf einem zweidimensionalen taktilen Braille-Display entwickelt, um eine m{\"o}glichst gleichberechtigte Teilhabe blinder Lernender an synchronen Lehrveranstaltungen zu erm{\"o}glichen. Nach einer ersten Evaluation mit blinden Probanden erfolgt die prototypische Umsetzung des Benutzungskonzepts f{\"u}r ein Open-Source-Klassenzimmer. Die abschließende Evaluation der prototypischen Umsetzung zeigt die Verbesserung der Zug{\"a}nglichkeit von virtuellen Klassenzimmern f{\"u}r blinde Lernende unter Verwendung eines taktilen Fl{\"a}chendisplays und best{\"a}tigt die Wirksamkeit der im Rahmen dieser Arbeit entwickelten Konzepte.},
  language  = {de}
}
@phdthesis{Waetzoldt2016,
  author    = {W{\"a}tzoldt, Sebastian},
  title     = {Modeling collaborations in adaptive systems of systems},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-97494},
  school      = {Universit{\"a}t Potsdam},
  pages     = {XII, 380},
  year      = {2016},
  abstract  = {Recently, due to an increasing demand on functionality and flexibility, beforehand isolated systems have become interconnected to gain powerful adaptive Systems of Systems (SoS) solutions with an overall robust, flexible and emergent behavior. The adaptive SoS comprises a variety of different system types ranging from small embedded to adaptive cyber-physical systems. On the one hand, each system is independent, follows a local strategy and optimizes its behavior to reach its goals. On the other hand, systems must cooperate with each other to enrich the overall functionality to jointly perform on the SoS level reaching global goals, which cannot be satisfied by one system alone. Due to difficulties of local and global behavior optimizations conflicts may arise between systems that have to be solved by the adaptive SoS. This thesis proposes a modeling language that facilitates the description of an adaptive SoS by considering the adaptation capabilities in form of feedback loops as first class entities. Moreover, this thesis adopts the Models@runtime approach to integrate the available knowledge in the systems as runtime models into the modeled adaptation logic. Furthermore, the modeling language focuses on the description of system interactions within the adaptive SoS to reason about individual system functionality and how it emerges via collaborations to an overall joint SoS behavior. Therefore, the modeling language approach enables the specification of local adaptive system behavior, the integration of knowledge in form of runtime models and the joint interactions via collaboration to place the available adaptive behavior in an overall layered, adaptive SoS architecture. Beside the modeling language, this thesis proposes analysis rules to investigate the modeled adaptive SoS, which enables the detection of architectural patterns as well as design flaws and pinpoints to possible system threats. Moreover, a simulation framework is presented, which allows the direct execution of the modeled SoS architecture. Therefore, the analysis rules and the simulation framework can be used to verify the interplay between systems as well as the modeled adaptation effects within the SoS. This thesis realizes the proposed concepts of the modeling language by mapping them to a state of the art standard from the automotive domain and thus, showing their applicability to actual systems. Finally, the modeling language approach is evaluated by remodeling up to date research scenarios from different domains, which demonstrates that the modeling language concepts are powerful enough to cope with a broad range of existing research problems.},
  language  = {en}
}
@phdthesis{Wust2015,
  author    = {Wust, Johannes},
  title     = {Mixed workload managment for in-memory databases},
  pages     = {VIII, 167},
  year      = {2015},
  language  = {en}
}
@phdthesis{Heise2014,
  author    = {Heise, Arvid},
  title     = {Data cleansing and integration operators for a parallel data analytics platform},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-77100},
  school      = {Universit{\"a}t Potsdam},
  pages     = {ii, 179},
  year      = {2014},
  abstract  = {The data quality of real-world datasets need to be constantly monitored and maintained to allow organizations and individuals to reliably use their data. Especially, data integration projects suffer from poor initial data quality and as a consequence consume more effort and money. Commercial products and research prototypes for data cleansing and integration help users to improve the quality of individual and combined datasets. They can be divided into either standalone systems or database management system (DBMS) extensions. On the one hand, standalone systems do not interact well with DBMS and require time-consuming data imports and exports. On the other hand, DBMS extensions are often limited by the underlying system and do not cover the full set of data cleansing and integration tasks. We overcome both limitations by implementing a concise set of five data cleansing and integration operators on the parallel data analytics platform Stratosphere. We define the semantics of the operators, present their parallel implementation, and devise optimization techniques for individual operators and combinations thereof. Users specify declarative queries in our query language METEOR with our new operators to improve the data quality of individual datasets or integrate them to larger datasets. By integrating the data cleansing operators into the higher level language layer of Stratosphere, users can easily combine cleansing operators with operators from other domains, such as information extraction, to complex data flows. Through a generic description of the operators, the Stratosphere optimizer reorders operators even from different domains to find better query plans. As a case study, we reimplemented a part of the large Open Government Data integration project GovWILD with our new operators and show that our queries run significantly faster than the original GovWILD queries, which rely on relational operators. Evaluation reveals that our operators exhibit good scalability on up to 100 cores, so that even larger inputs can be efficiently processed by scaling out to more machines. Finally, our scripts are considerably shorter than the original GovWILD scripts, which results in better maintainability of the scripts.},
  language  = {en}
}
@phdthesis{Neuhaus2017,
  author    = {Neuhaus, Christian},
  title     = {Sicherheitsmechanismen f{\"u}r dienstbasierte Softwaresysteme},
  school      = {Universit{\"a}t Potsdam},
  pages     = {183},
  year      = {2017},
  language  = {de}
}
@phdthesis{Kilic2016,
  author    = {Kilic, Mukayil},
  title     = {Vernetztes Pr{\"u}fen von elektronischen Komponenten {\"u}ber das Internet},
  school      = {Universit{\"a}t Potsdam},
  pages     = {104, XVI},
  year      = {2016},
  language  = {de}
}
@phdthesis{Dornhege2006,
  author    = {Dornhege, Guido},
  title     = {Increasing information transfer rates for brain-computer interfacing},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-7690},
  school      = {Universit{\"a}t Potsdam},
  year      = {2006},
  abstract  = {The goal of a Brain-Computer Interface (BCI) consists of the development of a unidirectional interface between a human and a computer to allow control of a device only via brain signals. While the BCI systems of almost all other groups require the user to be trained over several weeks or even months, the group of Prof. Dr. Klaus-Robert M{\"u}ller in Berlin and Potsdam, which I belong to, was one of the first research groups in this field which used machine learning techniques on a large scale. The adaptivity of the processing system to the individual brain patterns of the subject confers huge advantages for the user. Thus BCI research is considered a hot topic in machine learning and computer science. It requires interdisciplinary cooperation between disparate fields such as neuroscience, since only by combining machine learning and signal processing techniques based on neurophysiological knowledge will the largest progress be made. In this work I particularly deal with my part of this project, which lies mainly in the area of computer science. I have considered the following three main points: <b>Establishing a performance measure based on information theory:</b> I have critically illuminated the assumptions of Shannon's information transfer rate for application in a BCI context. By establishing suitable coding strategies I was able to show that this theoretical measure approximates quite well to what is practically achieveable. <b>Transfer and development of suitable signal processing and machine learning techniques:</b> One substantial component of my work was to develop several machine learning and signal processing algorithms to improve the efficiency of a BCI. Based on the neurophysiological knowledge that several independent EEG features can be observed for some mental states, I have developed a method for combining different and maybe independent features which improved performance. In some cases the performance of the combination algorithm outperforms the best single performance by more than 50 \%. Furthermore, I have theoretically and practically addressed via the development of suitable algorithms the question of the optimal number of classes which should be used for a BCI. It transpired that with BCI performances reported so far, three or four different mental states are optimal. For another extension I have combined ideas from signal processing with those of machine learning since a high gain can be achieved if the temporal filtering, i.e., the choice of frequency bands, is automatically adapted to each subject individually. <b>Implementation of the Berlin brain computer interface and realization of suitable experiments:</b> Finally a further substantial component of my work was to realize an online BCI system which includes the developed methods, but is also flexible enough to allow the simple realization of new algorithms and ideas. So far, bitrates of up to 40 bits per minute have been achieved with this system by absolutely untrained users which, compared to results of other groups, is highly successful.},
  subject      = {Kybernetik},
  language  = {en}
}