@book{VogelGiese2013, author = {Vogel, Thomas and Giese, Holger}, title = {Model-driven engineering of adaptation engines for self-adaptive software : executable runtime megamodels}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, isbn = {978-3-86956-227-8}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-63825}, publisher = {Universit{\"a}t Potsdam}, pages = {vi, 59}, year = {2013}, abstract = {The development of self-adaptive software requires the engineering of an adaptation engine that controls and adapts the underlying adaptable software by means of feedback loops. The adaptation engine often describes the adaptation by using runtime models representing relevant aspects of the adaptable software and particular activities such as analysis and planning that operate on these runtime models. To systematically address the interplay between runtime models and adaptation activities in adaptation engines, runtime megamodels have been proposed for self-adaptive software. A runtime megamodel is a specific runtime model whose elements are runtime models and adaptation activities. Thus, a megamodel captures the interplay between multiple models and between models and activities as well as the activation of the activities. In this article, we go one step further and present a modeling language for ExecUtable RuntimE MegAmodels (EUREMA) that considerably eases the development of adaptation engines by following a model-driven engineering approach. We provide a domain-specific modeling language and a runtime interpreter for adaptation engines, in particular for feedback loops. Megamodels are kept explicit and alive at runtime and by interpreting them, they are directly executed to run feedback loops. Additionally, they can be dynamically adjusted to adapt feedback loops. Thus, EUREMA supports development by making feedback loops, their runtime models, and adaptation activities explicit at a higher level of abstraction. Moreover, it enables complex solutions where multiple feedback loops interact or even operate on top of each other. Finally, it leverages the co-existence of self-adaptation and off-line adaptation for evolution.}, language = {en} } @book{SchwalbKruegerPlattner2013, author = {Schwalb, David and Kr{\"u}ger, Jens and Plattner, Hasso}, title = {Cache conscious column organization in in-memory column stores}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, isbn = {978-3-86956-228-5}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-63890}, publisher = {Universit{\"a}t Potsdam}, pages = {v, 84}, year = {2013}, abstract = {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.}, language = {en} } @book{RoggeSoltiMansvanderAalstetal.2013, author = {Rogge-Solti, Andreas and Mans, Ronny S. and van der Aalst, Wil M. P. and Weske, Mathias}, title = {Repairing event logs using stochastic process models}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, isbn = {978-3-86956-258-2}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-66797}, publisher = {Universit{\"a}t Potsdam}, pages = {19}, year = {2013}, abstract = {Companies strive to improve their business processes in order to remain competitive. Process mining aims to infer meaningful insights from process-related data and attracted the attention of practitioners, tool-vendors, and researchers in recent years. Traditionally, event logs are assumed to describe the as-is situation. But this is not necessarily the case in environments where logging may be compromised due to manual logging. For example, hospital staff may need to manually enter information regarding the patient's treatment. As a result, events or timestamps may be missing or incorrect. In this paper, we make use of process knowledge captured in process models, and provide a method to repair missing events in the logs. This way, we facilitate analysis of incomplete logs. We realize the repair by combining stochastic Petri nets, alignments, and Bayesian networks. We evaluate the results using both synthetic data and real event data from a Dutch hospital.}, language = {en} } @book{PufahlMeyerWeske2013, author = {Pufahl, Luise and Meyer, Andreas and Weske, Mathias}, title = {Batch regions : process instance synchronization based on data}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, isbn = {978-3-86956-280-3}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-69081}, publisher = {Universit{\"a}t Potsdam}, pages = {18}, year = {2013}, abstract = {Business process automation improves organizations' efficiency to perform work. In existing business process management systems, process instances run independently from each other. However, synchronizing instances carrying similar characteristics, i.e., sharing the same data, can reduce process execution costs. For example, if an online retailer receives two orders from one customer, there is a chance that they can be packed and shipped together to save shipment costs. In this paper, we use concepts from the database domain and introduce data views to business processes to identify instances which can be synchronized. Based on data views, we introduce the concept of batch regions for a context-aware instance synchronization over a set of connected activities. We also evaluate the concepts introduced in this paper with a case study comparing costs for normal and batch processing.}, language = {de} } @book{PapeTrefferHirschfeldetal.2013, author = {Pape, Tobias and Treffer, Arian and Hirschfeld, Robert and Haupt, Michael}, title = {Extending a Java Virtual Machine to Dynamic Object-oriented Languages}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, isbn = {978-3-86956-266-7}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-67438}, publisher = {Universit{\"a}t Potsdam}, pages = {163}, year = {2013}, abstract = {There are two common approaches to implement a virtual machine (VM) for a dynamic object-oriented language. On the one hand, it can be implemented in a C-like language for best performance and maximum control over the resulting executable. On the other hand, it can be implemented in a language such as Java that allows for higher-level abstractions. These abstractions, such as proper object-oriented modularization, automatic memory management, or interfaces, are missing in C-like languages but they can simplify the implementation of prevalent but complex concepts in VMs, such as garbage collectors (GCs) or just-in-time compilers (JITs). Yet, the implementation of a dynamic object-oriented language in Java eventually results in two VMs on top of each other (double stack), which impedes performance. For statically typed languages, the Maxine VM solves this problem; it is written in Java but can be executed without a Java virtual machine (JVM). However, it is currently not possible to execute dynamic object-oriented languages in Maxine. This work presents an approach to bringing object models and execution models of dynamic object-oriented languages to the Maxine VM and the application of this approach to Squeak/Smalltalk. The representation of objects in and the execution of dynamic object-oriented languages pose certain challenges to the Maxine VM that lacks certain variation points necessary to enable an effortless and straightforward implementation of dynamic object-oriented languages' execution models. The implementation of Squeak/Smalltalk in Maxine as a feasibility study is to unveil such missing variation points.}, language = {en} } @book{NeumannGiese2013, author = {Neumann, Stefan and Giese, Holger}, title = {Scalable compatibility for embedded real-time components via language progressive timed automata}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, isbn = {978-3-86956-226-1}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-63853}, publisher = {Universit{\"a}t Potsdam}, pages = {vi, 67}, year = {2013}, abstract = {The proper composition of independently developed components of an embedded real- time system is complicated due to the fact that besides the functional behavior also the non-functional properties and in particular the timing have to be compatible. Nowadays related compatibility problems have to be addressed in a cumbersome integration and configuration phase at the end of the development process, that in the worst case may fail. Therefore, a number of formal approaches have been developed, which try to guide the upfront decomposition of the embedded real-time system into components such that integration problems related to timing properties can be excluded and that suitable configurations can be found. However, the proposed solutions require a number of strong assumptions that can be hardly fulfilled or the required analysis does not scale well. In this paper, we present an approach based on timed automata that can provide the required guarantees for the later integration without strong assumptions, which are difficult to match in practice. The approach provides a modular reasoning scheme that permits to establish the required guarantees for the integration employing only local checks, which therefore also scales. It is also possible to determine potential configuration settings by means of timed game synthesis.}, language = {de} } @book{MeyerPufahlFahlandetal.2013, author = {Meyer, Andreas and Pufahl, Luise and Fahland, Dirk and Weske, Mathias}, title = {Modeling and enacting complex data dependencies in business processes}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, isbn = {978-3-86956-245-2}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-65103}, publisher = {Universit{\"a}t Potsdam}, pages = {40}, year = {2013}, abstract = {Enacting business processes in process engines requires the coverage of control flow, resource assignments, and process data. While the first two aspects are well supported in current process engines, data dependencies need to be added and maintained manually by a process engineer. Thus, this task is error-prone and time-consuming. In this report, we address the problem of modeling processes with complex data dependencies, e.g., m:n relationships, and their automatic enactment from process models. First, we extend BPMN data objects with few annotations to allow data dependency handling as well as data instance differentiation. Second, we introduce a pattern-based approach to derive SQL queries from process models utilizing the above mentioned extensions. Therewith, we allow automatic enactment of data-aware BPMN process models. We implemented our approach for the Activiti process engine to show applicability.}, language = {en} } @book{MeinelWillems2013, author = {Meinel, Christoph and Willems, Christian}, title = {openHPI : the MOOC offer at Hasso Plattner Institute}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, isbn = {978-3-86956-264-3}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-67176}, publisher = {Universit{\"a}t Potsdam}, pages = {21}, year = {2013}, abstract = {The new interactive online educational platform openHPI, (https://openHPI.de) from Hasso Plattner Institute (HPI), offers freely accessible courses at no charge for all who are interested in subjects in the field of information technology and computer science. Since 2011, "Massive Open Online Courses," called MOOCs for short, have been offered, first at Stanford University and then later at other U.S. elite universities. Following suit, openHPI provides instructional videos on the Internet and further reading material, combined with learning-supportive self-tests, homework and a social discussion forum. Education is further stimulated by the support of a virtual learning community. In contrast to "traditional" lecture platforms, such as the tele-TASK portal (http://www.tele-task.de) where multimedia recorded lectures are available on demand, openHPI offers didactic online courses. The courses have a fixed start date and offer a balanced schedule of six consecutive weeks presented in multimedia and, whenever possible, interactive learning material. Each week, one chapter of the course subject is treated. In addition, a series of learning videos, texts, self-tests and homework exercises are provided to course participants at the beginning of the week. The course offering is combined with a social discussion platform where participants have the opportunity to enter into an exchange with course instructors and fellow participants. Here, for example, they can get answers to questions and discuss the topics in depth. The participants naturally decide themselves about the type and range of their learning activities. They can make personal contributions to the course, for example, in blog posts or tweets, which they can refer to in the forum. In turn, other participants have the chance to comment on, discuss or expand on what has been said. In this way, the learners become the teachers and the subject matter offered to a virtual community is linked to a social learning network.}, language = {en} } @book{MeinelWillems2013, author = {Meinel, Christoph and Willems, Christian}, title = {openHPI : das MOOC-Angebot des Hasso-Plattner-Instituts}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, isbn = {978-3-86956-259-9}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-66802}, publisher = {Universit{\"a}t Potsdam}, pages = {22}, year = {2013}, abstract = {Die neue interaktive Online-Bildungsplattform openHPI (https://openHPI.de) des Hasso-Plattner-Instituts (HPI) bietet frei zug{\"a}ngliche und kostenlose Onlinekurse f{\"u}r interessierte Teilnehmer an, die sich mit Inhalten aus dem Bereich der Informationstechnologien und Informatik besch{\"a}ftige¬n. Wie die seit 2011 zun{\"a}chst von der Stanford University, sp{\"a}ter aber auch von anderen Elite-Universit{\"a}ten der USA angeboten „Massive Open Online Courses", kurz MOOCs genannt, bietet openHPI im Internet Lernvideos und weiterf{\"u}hrenden Lesestoff in einer Kombination mit lernunterst{\"u}tzenden Selbsttests, Hausaufgaben und einem sozialen Diskussionsforum an und stimuliert die Ausbildung einer das Lernen f{\"o}rdernden virtuellen Lerngemeinschaft. Im Unterschied zu „traditionellen" Vorlesungsportalen, wie z.B. dem tele-TASK Portal (http://www.tele-task.de), bei dem multimedial aufgezeichnete Vorlesungen zum Abruf bereit gestellt werden, bietet openHPI didaktisch aufbereitete Onlinekurse an. Diese haben einen festen Starttermin und bieten dann in einem austarierten Zeitplan von sechs aufeinanderfolgenden Kurswochen multimedial aufbereitete und wann immer m{\"o}glich interaktive Lehrmaterialien. In jeder Woche wird ein Kapitel des Kursthemas behandelt. Dazu werden zu Wochenbeginn eine Reihe von Lehrvideos, Texten, Selbsttests und ein Hausaufgabenblatt bereitgestellt, mit denen sich die Kursteilnehmer in dieser Woche besch{\"a}ftigen. Kombiniert sind die Angebote mit einer sozialen Diskussionsplattform, auf der sich die Teilnehmer mit den Kursbetreuern und anderen Teilnehmern austauschen, Fragen kl{\"a}ren und weiterf{\"u}hrende Themen diskutieren k{\"o}nnen. Nat{\"u}rlich entscheiden die Teilnehmer selbst {\"u}ber Art und Umfang ihrer Lernaktivit{\"a}ten. Sie k{\"o}nnen in den Kurs eigene Beitr{\"a}ge einbringen, zum Beispiel durch Blogposts oder Tweets, auf die sie im Forum verweisen. Andere Lernende k{\"o}nnen diese dann kommentieren, diskutieren oder ihrerseits erweitern. Auf diese Weise werden die Lernenden, die Lehrenden und die angebotenen Lerninhalte in einer virtuellen Gemeinschaft, einem sozialen Lernnetzwerk miteinander verkn{\"u}pft.}, language = {de} } @book{HerzbergWeske2013, author = {Herzberg, Nico and Weske, Mathias}, title = {Enriching raw events to enable process intelligence : research challenges}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, isbn = {978-3-86956-241-4}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-64012}, publisher = {Universit{\"a}t Potsdam}, pages = {30}, year = {2013}, abstract = {Business processes are performed within a company's daily business. Thereby, valuable data about the process execution is produced. The quantity and quality of this data is very dependent on the process execution environment that reaches from predominantly manual to fullautomated. Process improvement is one essential cornerstone of business process management to ensure companies' competitiveness and relies on information about the process execution. Especially in manual process environments data directly related to the process execution is rather sparse and incomplete. In this paper, we present an approach that supports the usage and enrichment of process execution data with context data - data that exists orthogonally to business process data - and knowledge from the corresponding process models to provide a high-quality event base for process intelligence subsuming, among others, process monitoring, process analysis, and process mining. Further, we discuss open issues and challenges that are subject to our future work.}, language = {de} }