@book{MeinelSack2012, author = {Meinel, Christoph and Sack, Harald}, title = {Internetworking : technische Grundlagen und Anwendungen}, publisher = {Springer-Verlag Berlin Heidelberg}, address = {Berlin, Heidelberg}, isbn = {978-3-540-92939-0}, doi = {10.1007/978-3-540-92940-6}, pages = {978 S.}, year = {2012}, language = {de} } @phdthesis{Ghasemzadeh2005, author = {Ghasemzadeh, Mohammad}, title = {A new algorithm for the quantified satisfiability problem, based on zero-suppressed binary decision diagrams and memoization}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-6378}, school = {Universit{\"a}t Potsdam}, year = {2005}, abstract = {Quantified Boolean formulas (QBFs) play an important role in theoretical computer science. QBF extends propositional logic in such a way that many advanced forms of reasoning can be easily formulated and evaluated. In this dissertation we present our ZQSAT, which is an algorithm for evaluating quantified Boolean formulas. ZQSAT is based on ZBDD: Zero-Suppressed Binary Decision Diagram , which is a variant of BDD, and an adopted version of the DPLL algorithm. It has been implemented in C using the CUDD: Colorado University Decision Diagram package. The capability of ZBDDs in storing sets of subsets efficiently enabled us to store the clauses of a QBF very compactly and let us to embed the notion of memoization to the DPLL algorithm. These points led us to implement the search algorithm in such a way that we could store and reuse the results of all previously solved subformulas with a little overheads. ZQSAT can solve some sets of standard QBF benchmark problems (known to be hard for DPLL based algorithms) faster than the best existing solvers. In addition to prenex-CNF, ZQSAT accepts prenex-NNF formulas. We show and prove how this capability can be exponentially beneficial.}, subject = {Bin{\"a}res Entscheidungsdiagramm}, language = {en} } @phdthesis{Linckels2008, author = {Linckels, Serge}, title = {An e-librarian service : supporting explorative learning by a description logics based semantic retrieval tool}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17452}, school = {Universit{\"a}t Potsdam}, year = {2008}, abstract = {Although educational content in electronic form is increasing dramatically, its usage in an educational environment is poor, mainly due to the fact that there is too much of (unreliable) redundant, and not relevant information. Finding appropriate answers is a rather difficult task being reliant on the user filtering of the pertinent information from the noise. Turning knowledge bases like the online tele-TASK archive into useful educational resources requires identifying correct, reliable, and "machine-understandable" information, as well as developing simple but efficient search tools with the ability to reason over this information. Our vision is to create an E-Librarian Service, which is able to retrieve multimedia resources from a knowledge base in a more efficient way than by browsing through an index, or by using a simple keyword search. In our E-Librarian Service, the user can enter his question in a very simple and human way; in natural language (NL). Our premise is that more pertinent results would be retrieved if the search engine understood the sense of the user's query. The returned results are then logical consequences of an inference rather than of keyword matchings. Our E-Librarian Service does not return the answer to the user's question, but it retrieves the most pertinent document(s), in which the user finds the answer to his/her question. Among all the documents that have some common information with the user query, our E-Librarian Service identifies the most pertinent match(es), keeping in mind that the user expects an exhaustive answer while preferring a concise answer with only little or no information overhead. Also, our E-Librarian Service always proposes a solution to the user, even if the system concludes that there is no exhaustive answer. Our E-Librarian Service was implemented prototypically in three different educational tools. A first prototype is CHESt (Computer History Expert System); it has a knowledge base with 300 multimedia clips that cover the main events in computer history. A second prototype is MatES (Mathematics Expert System); it has a knowledge base with 115 clips that cover the topic of fractions in mathematics for secondary school w.r.t. the official school programme. All clips were recorded mainly by pupils. The third and most advanced prototype is the "Lecture Butler's E-Librarain Service"; it has a Web service interface to respect a service oriented architecture (SOA), and was developed in the context of the Web-University project at the Hasso-Plattner-Institute (HPI). Two major experiments in an educational environment - at the Lyc{\´e}e Technique Esch/Alzette in Luxembourg - were made to test the pertinence and reliability of our E-Librarian Service as a complement to traditional courses. The first experiment (in 2005) was made with CHESt in different classes, and covered a single lesson. The second experiment (in 2006) covered a period of 6 weeks of intensive use of MatES in one class. There was no classical mathematics lesson where the teacher gave explanations, but the students had to learn in an autonomous and exploratory way. They had to ask questions to the E-Librarian Service just the way they would if there was a human teacher.}, subject = {Terminologische Logik}, language = {en} } @phdthesis{Huang2006, author = {Huang, Wanjun}, title = {Temporary binding for dynamic middleware construction and web services composition}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-7672}, school = {Universit{\"a}t Potsdam}, year = {2006}, abstract = {With increasing number of applications in Internet and mobile environments, distributed software systems are demanded to be more powerful and flexible, especially in terms of dynamism and security. This dissertation describes my work concerning three aspects: dynamic reconfiguration of component software, security control on middleware applications, and web services dynamic composition. Firstly, I proposed a technology named Routing Based Workflow (RBW) to model the execution and management of collaborative components and realize temporary binding for component instances. The temporary binding means component instances are temporarily loaded into a created execution environment to execute their functions, and then are released to their repository after executions. The temporary binding allows to create an idle execution environment for all collaborative components, on which the change operations can be immediately carried out. The changes on execution environment will result in a new collaboration of all involved components, and also greatly simplifies the classical issues arising from dynamic changes, such as consistency preserving etc. To demonstrate the feasibility of RBW, I created a dynamic secure middleware system - the Smart Data Server Version 3.0 (SDS3). In SDS3, an open source implementation of CORBA is adopted and modified as the communication infrastructure, and three secure components managed by RBW, are created to enhance the security on the access of deployed applications. SDS3 offers multi-level security control on its applications from strategy control to application-specific detail control. For the management by RBW, the strategy control of SDS3 applications could be dynamically changed by reorganizing the collaboration of the three secure components. In addition, I created the Dynamic Services Composer (DSC) based on Apache open source projects, Apache Axis and WSIF. In DSC, RBW is employed to model the interaction and collaboration of web services and to enable the dynamic changes on the flow structure of web services. Finally, overall performance tests were made to evaluate the efficiency of the developed RBW and SDS3. The results demonstrated that temporary binding of component instances makes slight impacts on the execution efficiency of components, and the blackout time arising from dynamic changes can be extremely reduced in any applications.}, subject = {Middleware}, language = {en} } @inproceedings{DennertMoellerGarmannKujathetal.2016, author = {Dennert-M{\"o}ller, Elisabeth and Garmann, Robert and Kujath, Bertold and Zscheyge, Oliver and Weicker, Karsten and B{\"o}hne, Sebastian and Knobelsdorf, Maria and Kreitz, Christoph and Steen, Alexander and Wisniewski, Max and Benzm{\"u}ller, Christoph and Gebhardt, Kai and Ehlenz, Matthias and Bergner, Nadine and Schroeder, Ulrik}, title = {Hochschuldidaktik der Informatik}, editor = {Schwill, Andreas and Lucke, Ulrike}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, isbn = {978-3-86956-376-3}, issn = {1868-0844}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-93511}, pages = {102}, year = {2016}, abstract = {Die 7. Fachtagung f{\"u}r Hochschuldidaktik, die 2016 erneut mit der DeLFI E-Learning Fachtagung Informatik stattfand, setzte das erfolgreiche Modell einer Tagung fort, die sich mit hochschuldidaktischen Fragen und der Gestaltung von Studieng{\"a}ngen der Informatik besch{\"a}ftigt. Thema der Tagung waren alle Fragen, die sich der Vermittlung von Informatikgegenst{\"a}nden im Hochschulbereich widmen. Dazu geh{\"o}rten u.a.: • fachdidaktische Konzepte der Vermittlung einzelner Informatikgegenst{\"a}nde • methodische L{\"o}sungen, wie spezielle Lehr- und Lernformen, Durchf{\"u}hrungskonzepte • empirische Ergebnisse und Vergleichsstudien • E-Learning-Ans{\"a}tze, wenn sie ein erkennbares didaktisches Konzept verfolgen • Studienkonzepte und Curricula, organisatorische Fragen, wie Gewinnung von Studierenden, Studieneingangsphase, Abbrecher. Die Fachtagung widmete sich ausgew{\"a}hlten Fragestellungen dieses Themenkomplexes, die durch Vortr{\"a}ge ausgewiesener Experten, durch eingereichte Beitr{\"a}ge und durch Pr{\"a}sentationen und Poster intensiv behandelt wurden. Unser besonderer Dank gilt dem Programmkomitee und den hier nicht genannten Helfern f{\"u}r ihren Einsatz bei der Vorbereitung und Durchf{\"u}hrung der Tagung.}, language = {de} } @phdthesis{Menzel2011, author = {Menzel, Michael}, title = {Model-driven security in service-oriented architectures : leveraging security patterns to transform high-level security requirements to technical policies}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-59058}, school = {Universit{\"a}t Potsdam}, year = {2011}, abstract = {Service-oriented Architectures (SOA) facilitate the provision and orchestration of business services to enable a faster adoption to changing business demands. Web Services provide a technical foundation to implement this paradigm on the basis of XML-messaging. However, the enhanced flexibility of message-based systems comes along with new threats and risks. To face these issues, a variety of security mechanisms and approaches is supported by the Web Service specifications. The usage of these security mechanisms and protocols is configured by stating security requirements in security policies. However, security policy languages for SOA are complex and difficult to create due to the expressiveness of these languages. To facilitate and simplify the creation of security policies, this thesis presents a model-driven approach that enables the generation of complex security policies on the basis of simple security intentions. SOA architects can specify these intentions in system design models and are not required to deal with complex technical security concepts. The approach introduced in this thesis enables the enhancement of any system design modelling languages - for example FMC or BPMN - with security modelling elements. The syntax, semantics, and notion of these elements is defined by our security modelling language SecureSOA. The metamodel of this language provides extension points to enable the integration into system design modelling languages. In particular, this thesis demonstrates the enhancement of FMC block diagrams with SecureSOA. To enable the model-driven generation of security policies, a domain-independent policy model is introduced in this thesis. This model provides an abstraction layer for security policies. Mappings are used to perform the transformation from our model to security policy languages. However, expert knowledge is required to generate instances of this model on the basis of simple security intentions. Appropriate security mechanisms, protocols and options must be chosen and combined to fulfil these security intentions. In this thesis, a formalised system of security patterns is used to represent this knowledge and to enable an automated transformation process. Moreover, a domain-specific language is introduced to state security patterns in an accessible way. On the basis of this language, a system of security configuration patterns is provided to transform security intentions related to data protection and identity management. The formal semantics of the security pattern language enable the verification of the transformation process introduced in this thesis and prove the correctness of the pattern application. Finally, our SOA Security LAB is presented that demonstrates the application of our model-driven approach to facilitate a dynamic creation, configuration, and execution of secure Web Service-based composed applications.}, language = {en} } @misc{KliemeTietzMeinel2018, author = {Klieme, Eric and Tietz, Christian and Meinel, Christoph}, title = {Beware of SMOMBIES}, series = {The 17th IEEE International Conference on Trust, Security and Privacy in Computing and Communications (IEEE TrustCom 2018)/the 12th IEEE International Conference on Big Data Science and Engineering (IEEE BigDataSE 2018)}, journal = {The 17th IEEE International Conference on Trust, Security and Privacy in Computing and Communications (IEEE TrustCom 2018)/the 12th IEEE International Conference on Big Data Science and Engineering (IEEE BigDataSE 2018)}, publisher = {IEEE}, address = {New York}, isbn = {978-1-5386-4387-7}, issn = {2324-9013}, doi = {10.1109/TrustCom/BigDataSE.2018.00096}, pages = {651 -- 660}, year = {2018}, abstract = {Several research evaluated the user's style of walking for the verification of a claimed identity and showed high authentication accuracies in many settings. In this paper we present a system that successfully verifies a user's identity based on many real world smartphone placements and yet not regarded interactions while walking. Our contribution is the distinction of all considered activities into three distinct subsets and a specific one-class Support Vector Machine per subset. Using sensor data of 30 participants collected in a semi-supervised study approach, we prove that unsupervised verification is possible with very low false-acceptance and false-rejection rates. We furthermore show that these subsets can be distinguished with a high accuracy and demonstrate that this system can be deployed on off-the-shelf smartphones.}, language = {en} } @article{ThienenNoweskiMeineletal.2012, author = {Thienen, Julia von and Noweski, Christine and Meinel, Christoph and Lang, Sabine and Nicolai, Claudia and Bartz, Andreas}, title = {What can design thinking learn from behavior group theraphy?}, isbn = {978-3-642-31990-7}, year = {2012}, language = {en} } @misc{MeinelSack2004, author = {Meinel, Christoph and Sack, Harald}, title = {WWW : Kommunikation, Internetworking, Web-Technologien}, publisher = {Springer}, address = {Berlin}, isbn = {3-540-44276-6}, issn = {1439-5428}, pages = {1179 S.}, year = {2004}, language = {de} } @book{MeinelSack2009, author = {Meinel, Christoph and Sack, Harald}, title = {Digitale Kommunikation : Vernetzen, Multimedia, Sicherheit}, series = {Media Press}, journal = {Media Press}, publisher = {Springer-Verlag Berlin Heidelberg}, address = {Berlin, Heidelberg}, isbn = {978-3-540-92922-2}, issn = {1439-3107}, doi = {10.1007/978-3-540-92923-9}, pages = {422 S.}, year = {2009}, language = {de} }