University of Siegen

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End date: 2009Subject: search.filters.subject.004 Informatik

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    PublicationAccess status: Open Access ,
    DeLFI 2007 : die 5. e-Learning Fachtagung Informatik, 17. - 20. September 2007 an der Universität Siegen
    (2007)
    Dieser Tagungsband enthält einen der zwei eingeladenen Vorträge und 23 Beiträge, die vom Programmkomitee aus 46 eingereichten Beiträgen nach einem wissenschaftlichen Begutachtungsprozess ausgewählt wurden. Diese Beiträge beleuchten die folgenden Schwerpunkte der Tagung aus unterschiedlichen Perspektiven: Didaktik des E-Learning, Content-Engineering, Fallstudien & Erfahrungsberichte, Infrastrukturen & Mobilität und Kollaboration. Eine Abrundung erfährt der Tagungsband durch acht zweiseitige Kurzbeiträge, die aktuelle Entwicklungen aufgreifen. Im Rahmen der Konferenz finden drei Workshops mit eigenen Publikationen statt: Web 2.0 and Social Software in Technology enhanced Learning, Rechnerunterstütztes Selbststudium in der Informatik, E-Learning und Literatur.
    Source Type:Conference Proceedings
    Series:GI-Edition : Proceedings
    Volume number:111
      3  8
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    PublicationAccess status: Open Access ,
    Didaktik der Informatik in Theorie und Praxis : 12. GI-Fachtagung "Informatik und Schule - INFOS 2007", 19. - 21. September 2007 an der Universität Siegen
    (2007)
    Dieser Tagungsband enthält vier eingeladene Vorträge und 23 Beiträge, die vom Programmkomitee aus 46 eingereichten Beiträgen nach einem wissenschaftlichen Begutachtungsprozess ausgewählt wurden. Diese Beiträge beleuchten die folgenden Schwerpunkte der Tagung aus unterschiedlichen Perspektiven: Studium und Fortbildung, Informatiksysteme als Unterrichtsmittel, Forschungsansätze, Fundamentale Ideen in der Unterrichtspraxis, Anwendungsorientierter Informatikunterricht, Qualitätsentwicklung und Qualitätssicherung im Informatikunterricht. Eine Abrundung erfährt der Tagungsband durch acht zweiseitige Kurzbeiträge und die Vorträge des 7. Workshops "Didaktik der Informatik aktuelle Forschungsergebnisse". Im Rahmen der Konferenz finden außerdem 26 weitere Workshops und drei thematische Fortbildungen statt.
    Source Type:Conference Proceedings
    Series:GI-Edition : Proceedings
    Volume number:112
      1  8
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    PublicationAccess status: Open Access ,
    Understanding and designing appropriation infrastructures : artifacts as boundary objects in the continuous software development
    (2009)
    Stevens, Gunnar
    Co-production among product communities has turned out to be a major challenge for the software industry. There is a growing need for evolutionary development strategies sup-plemented by means of interweaving software production and software use more efficiently. In this scenario, the Internet offers a ubiquitous transportation infrastructure for digital products, and impacts the communication culture. However, opportunities to mediate between consumption and production (needs and solutions respectively) within software communities are under-investigated, empirically, theoretically and in terms of design methodologies. Framing the design issue to enable new forms of co-production, I investigate in the first part of my thesis the corresponding theoretical problem of mediating innovation development. From a Marxian understanding of appropriation, I show how philosophical, sociological, and technological aspects of mediation are related to each other in the case of innovation development. Moreover, the diverse theoretical positions in Design Science research suggested in literature can be compared in respect to the question of mediating needs and solutions. Regarding this question, I develop a personal Pragmatistic position rooted in a dialectical understanding of praxis, which synthesizes different non-positivistic streams in IT research (especially Wulf/Pipek, Orlikowski, Suchman, Star, and Rit-tel/Webber). My theoretical studies imply a paradigm shift in user-centered innovation research. Com-plementing studies on individual motivations for user innovations, my thesis uncover the work structure of making wicked situations accountable across social worlds to generate situated innovations. From this position I figure out the role of the socio-material artifact as a boundary object mediating distributed appropriation and production. In the second part of my thesis I demonstrate how the analysis of wicked situations can be interpreted in terms of design. I present my concept of Appropriation Infrastructure, which is a novel design solution for interweaving distributed production and use, based on the specific qualities of digital products. Implementing a first instance of Appropriation Infrastructures, I follow a user-centered approach that supports the appropriation work in its situated and social dimension. In the tradition of End User Development (EUD) it supports users to change the material and the symbolic construction of software artifacts and - going beyond traditional EUD approaches - to articulate these situated development across product communities. In my solution, EUD-tools are interwoven in the context of a wicked situation to inquiry into the situation as well as in the design of situated innovations. Here, the artifact present-at-hand serves as a boundary object to mediate and translate a diversity of meaning constructions and to make the innovative potential of a wicked situation accountable. To support the situational talk-back of the user as a reflective practitioner thinking about wicked situations, rooms for private conversations are offered and options are provided to integrate colleagues and friends, as well as a public product community. I have evaluated this first instance of Appropriation Infrastructure by means of a long-term study focused on users and designers and their mediated activities. Taken as a whole, my thesis presents a theoretical model of appropriation and a technical solution for appropriation support, which shows how non-positivistic Information System research can be combined with Design Science research to support new forms of co-production within software communities.
    Source Type:Doctoral Thesis
      2  3
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    PublicationAccess status: Open Access ,
    Metadaten-Management in crossmedialen Produktionsumgebungen : semantikinvariante bidirektionale Transformation typographischer Auszeichnungen auf Basis variabler Compiler
    (2009)
    Harlessem, Marcus von
    In the field of Cross Media Publishing (CMP) the processes of two separate application suits require integration: first, the online information processing via Web Content Management Systems (WCMS) and similar applications, and, second, the traditional printed publications, such as the layout and formatting with Desktop-Publishing Systems (DTP). After many years of respective isolation, much effort has been dedicated to enable data transfers between these realms. One major achievement was XML as a data transport protocol. XML, and the sub-languages derived from it, addressed many of the resultant problems. In the wake of media convergence, these integration processes get a fast-growing importance. In the context of their diversification strategies, media enterprises require the multiple utilization of their expensive content with the lowest possible costs. The aim of this work was, first, to identify and formalize the risks and the costs of the new processes, that would occur in a media-neutral processing environment information. While the theory of the processes of media-neutral image processing has already been solved, so far there were no satisfactory solutions for the treatment of typographical metadata, if the industry standards for handling content are maintained and users would be allowed to work in their familiar application frameworks. Every single media-specific application for editing and layout of textual content has its own internal language, with typographic syntax and semantics. In order not to lose this typographic metadata while transferring content between the media-specific applications or at the multiple use of texts within a media class, it was in the scope of this work to develop a translation-procedure for typographical metadata, based on translators controlled by grammar rules. For the exchange of textual data, the compilers uses the Typographic Markup Language (TML), an XML-based dialect of the media-neutral contents representation, as an intermediate hub format of the typographical metadata. Developing the TML was also an aspect of this work. For this work, the demands for the overall architecture have been predefined in collaboration with the InterRed GmbH. InterRed is a software manufacturer, that develops and distributes an editing and publishing application for the media independent publishing of content such as text, images and video. For the bi-directional exchange of text content between the editorial system and industry standards such as QuarkXPress, Adobe InDesign, RTF or HTML there was no method, which takes the semantics of a typographical text into account.
    Source Type:Doctoral Thesis
      3  8
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    PublicationAccess status: Open Access ,
    Real-time particle systems and their application to flow visualization
    (2009)
    Cuntz, Nicolas
    Both visualization and simulation tasks make high demands on accuracy and interactivity. The former is an evident requisite of any tool focusing on quality, the latter stands for a responsive system in which the user has real-time control. A permanent trade-off between both demands can be observed, since high accuracy is usually time-consuming. The graphics processing unit (GPU), which evolved to a powerful general purpose coprocessor during the last decade, is undoubtedly becoming an ideal instrument for performing visualization and simulation tasks accurately and in real-time. One of the main challenges in the context of geometric flow visualization and fluid dynamics is the representation of motion. In both fields, particle systems and grid-based structures constitute basic models describing the objects to which the motion is applied. This work is dedicated to the development of GPU-based particle techniques and their combination with grids in order to improve the efficiency of fluid simulation and geometric flow visualization techniques. All resulting algorithms are characterized by their parallel nature and by being entirely executable on graphics hardware. The first aim is to provide an efficient solution to particle coupling in the context of fluids based on smoothed particle hydrodynamics. A parallel processing using graphics hardware is achieved by providing a grid-based mechanism for the efficient processing of particle neighborhoods. The second aim is to provide a set of algorithms for various geometric flow visualization techniques including flow particles, flow lines and flow surfaces/volumes. The accuracy is explicitly addressed in all cases. Accordingly, a method for generating time-adaptive stream and path lines and a special refinement scheme for streak lines is presented. The flow volumes, including time surfaces, path and streak volumes, are based on a parallel reinterpretation of the particle level set (PLS) method. This reinterpretation is based on a method for grid-particle interchange which is similar to the one proposed for particle coupling. Combining a grid and a particle set takes the advantages from both models: the grid representation is robust w.r.t. deformations and topological changes, and the particles are used to reduce numerical diffusion. For the reinitialization of the level set function, which is the most time-consuming step of the PLS algorithm, a hierarchical method for computing distance transforms is proposed. It turns out that the use of a distance transform is advantageous for realizing a GPU-based PLS framework.
    Source Type:Doctoral Thesis
      1  4
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    PublicationAccess status: Open Access ,
    Modellierung des Online-Steerings von Gridjobs als Zugriffe auf verteilten gemeinsamen Speicher
    (2009)
    Lorenz, Daniel
    In this work, four tasks for online steering are distinguished: Communication, data consistency, automated evaluation and optimization, and data access. The focus of this work is on the data consistency task. For this task, a new model is presented, which views online steering as accesses to data in a virtual distributed shared memory. To ensure the consistency of the data, the intra-process condition and the inter-process condition are identified. Both define rules for the data exchange. Dependent on the requirements of the application, both conditions must be satisfied or only the intra-process condition must be satisfied. Two consistency models are defined which satisfy the intra-process condition which are named special weak consistency and delayed weak consistency. Based on an algorithm from CUMULVS, the schedule consistency is defined which satisfies both conditions. Furthermore, data objects may exist for which none of the conditions must be fullfilled. When using the special weak consistency or the delayed weak consistency, only pairs consisting of one application process and one steering process communicate. For both models, an update protocol and an invalidate protocol are developed and implemented. Additionally, an update protocol and an invalidate protocol for the PRAM consistency are implemented. With the implementations the behavior of the protocol was evaluated. Hereby, it was detected that the protocols of the special weak consistency were slower than the protocols of the delayed weak consistency. The performance difference increases if the round trip time in the network increases. For online steering of Gridjobs, a possibility must exist to communicate with a Gridjob. In this work, a communication channel is developed which allow to establish a secure communication connection to a Gridjob without compromising the security of the site. Several scenarios are developed for establishing a communication channel, depending on the site's configuration. The appropriate scenario can be automatically detected. The throughput and the round trip time of the communication channel are evaluated using different scenarios and security levels. The behavior of the communication channel can be modeled with a pipeline. The throughput is limited by the slowest pipeline stage. When using encryption, the throughput between German LCG-sites is limited by the computing time for encryption/decryption on the endpoints of the communication. When using two security levels without encryption, the bandwidth limits the throughput for one-directional data transfer. In the case of two-directional data transfer, the computing time at the endpoints can limit the throughput. Every component adds a constant to the round trip time. Compared to the round trip time between sites, the additional contributions are negligible. Optimization and data access are not discussed in the same level of detail than data consistency and communication. The presented optimization approaches are based on the assumption that the bandwidth are limiting the performance. The optimization selects the invalidate or update protocol based on predictions of their performance. The goal of the data access task is, to intercept data accesses to steered date objects and call methods of the steering system in order to allow the steering system to react on data accesses. Hereby, classifications are made which discern the possibilities of the steering system to react on the data accesses. With the implementation of the steering model in RMOST, jobs of the ATLAS experiment can be steered.
    Source Type:Doctoral Thesis
      3  4
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    PublicationAccess status: Open Access ,
    Entwicklung und Erprobung des didaktischen Systems Internetworking im Informatikunterricht
    (2009)
    Freischlad, Stefan
    Internet-based informatics systems increasingly influence real-life situations. Competencies for Internet applications and services have to be explicitly attained because not observable processes and invisible structures have to be considered. There are examples of successful learning processes for selected parts of the Internet. A systematic analysis of educational requirements and a derived didactic concept for general education is missing. An overall didactic concept for informatics in secondary education is presented in this work, which contributes to goal-oriented and responsible application of the Internet. This work comprises the process from analysis of necessary competencies to realisation of learning processes in classes in secondary education. The contribution of informatics to identified competencies is examined and educational requirements are determined. Recommendations for informatics education and research results of successfully introduced classes are analysed with regard to the learning objectives. Informatics courses support the development of competencies related to Internet-based digital media. The development of a didactic concept concerning Internetworking is described. The approach of Didactic Systems is examined, elaborated, and transferred to Internetworking. The theory-based approach is realised in practice during four classroom projects. Relations between concepts about Internetworking are analysed, applied to plan classroom projects, and evaluated by means of knowledge networks. Learning activities are described on the basis of exercise classes, which represent the necessary knowledge to solve an exercise. Properties of exercises are described and utilised. Learning activities that were not realizable up to this point are facilitated by the developed learning software Filius. The reduction of complexity of real informatics systems by simulation and the selection of appropriate views of the object of examination are based on results of didactics of informatics. Classroom projects are performed to explore learning processes and to evaluate the Didactic System Internetworking. Learning processes are put into practice based on the theoretic approach. Minimal objectives for the classroom projects are determined from educational guidelines of informatics in secondary education at North Rhine-Westfalia. The methodical design of the learning processes is based on the guidelines and general requirements of didactics of informatics. Activity-oriented learning material is selected and introduced into practice to examine learning processes. Identified learning difficulties result in modification of the knowledge structures and are considered during the development of Filius. Further findings allow conclusions regarding the necessity of exercises of identified exercise classes and regarding the applicability of determined exercise properties to design assignments to define the outcome of learning processes. The classroom projects confirm the viability of the Didactic System Internetworking and contribute to further analysis of the development of competencies in informatics education. The Didactic System Internetworking provides a theory-based empirically approved didactic concept for the development of competencies to establish and to use Internet-based informatics systems.
    Source Type:Doctoral Thesis
      7  9
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    PublicationAccess status: Open Access ,
    Concepts elaboration and system architectures for mining very large image archives
    (2009)
    Gómez Muñoz, Inés María
    During the last decades, satellite technology has been outstandingly improved, providing huge amounts of Earth Observation (EO) data to be processed and stored. The availability of very high resolution sensors has encouraged the birth of new domains for remote sensing applications. Relatively new fields in this frame are Image Information Mining (IIM) and Content Based Image Retrieval (CBIR). These fields are born to provide solutions for querying very large EO archives by content. This dissertation tries to contribute on the IIM domain, providing new image processing algorithms and optimization processes for mining image databases. The study of an IIM system can be focused on signal processing methods, data compression, semantic knowledge discovery, human-machine interaction or system architecture design. Thus, the system can be divided in three modules: on one hand, we have the off-line tasks, consisting of signal and image processing methods. The extracted information of these algorithms is based on a hierarchical Bayesian representation, and usually, is very time consuming. On the other hand, we explore the on-line actions that are performed at real time through an interaction with the user. Finally, an optimal software architecture where all these concepts are merged has to be studied. In this thesis, contributions on these three modules are provided. We begin studying multi temporal high resolution image analysis under different illumination conditions and strong background clutter. The aim is to build a target detection map through a synergy of image processing methods. However, we can be faced with a common problem while extracting information from EO data, which is the estimation of parameters. Often the accuracy of the methods is strongly dependent on the selection of parameters and it is difficult to a priori know the optimum one. This is the motivation for the second contribution that deals with this problem. To cope with it, we implement an algorithm based on clustering features that uses information and rate distortion theories to help in the assessment of parameters. One of the main characteristics of an IIM system, is its potential to learn though human interaction. The user provides some examples of his interests, and based on them, the system learns his preferences, searches for them in large archives, and returns similar contents to the user provided ones. In this framework, we developed a multiple classifier, that enables the user to provide more than one example type. Thus, the system will be queried for different features, refining the query results and search accuracy. In order to be an operable and useful system, all new features proposed in this dissertation have to be accomplished in a modular system architecture. The system, from the software design point of view, must be opened, standard compliant and accessible though Internet. The software architecture design of the IIM system is the last contribution of this thesis. For building the system, we have to consider the following aspects: - how to manage the large data volume of original and processed images; - the automatization of tasks as loading new data, extracting features or generation of thematic maps; - how to adapt the system to the user knowledge, that is, the image interpretation has to be adapted to the symbols the users are able to recognize and to the specific semantics of their domains; - how to perform the man-machine communication through a continuous interaction and exchange of knowledge.
    Source Type:Doctoral Thesis
      1  5
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    PublicationAccess status: Open Access ,
    Crystal Ball : die Gewinnung von verwertbarer Information aus Datenobjekten mit unscharfem Zusammenhang
    (2009)
    Montino, Ralf
    In times of globalization opportunities but also challenges are rising for the enterprises. The permanent competition requires continuous improvement of products and processes from all companies. The companies can set themselves apart from the market by better quality. Beside the increase in customer satisfaction, improvement of quality leads to reduced costs by higher reliability in planning and reduced scrap. A rising competiveness of the company is the result. The production of parts for the automotive industry has been faced with very high quality demands for a long time. Taking the semiconductor industry as example, the state of the art will be described. Reproducing single process steps -which have been defined as correct before- as identical as necessary is the main target of tools and procedures which are currently used. Especially in very complex production processes, the impact of variations in a single process step for the final product is often not clear. Many companies -from small ones to the very big ones- made a lot of efforts together with universities and institutes. They searched for solutions to deal with the huge amounts of data and they tried to gain useful information from this data. The focal point of this work is the retrieval of root causes for deviations in a very complex production environment. Because of the huge amount of influencing parameters and the long production time, an analytical solution does not lead to the target. As described in the literature, Neural Networks are often used for classification purposes or for prediction of the behavior of complex systems. In this elaboration, a Neural Network is used to find the root cause for the system behavior. Also new is data reduction by Feature Selection, whereas the Neural Network acts as validation instance for the selected parameters. No knowledge about the technical dependencies is being used in this process. So, no possible solutions are excluded in advance. With this combination of data reduction (Feature Selection) and knowledge generation (Neural Network), the relevant input parameters for the analyzed effect can be identified successfully. Furthermore, the rules of the Neural Network provide hints for process optimization and error prevention. At first, this newly developed method has been validated successfully with synthetic data. After that, the system has been used with real production data obtaining convincing results. Analyzing one problem as an example, more than 1000 datasets from one product were selected. The system identified a small number of parameter responsible for the effect from a bunch of nearly 100. Actually, the method is being implemented at a semiconductor manufacturer. Other companies show interest in this method. Beyond that, an implementation of this method seems to be reasonable in other parts of the economy, especially when there are business processes with a combination of high quality requirements and a very good documentation of these processes.
    Source Type:Doctoral Thesis
      1  7
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    PublicationAccess status: Open Access ,
    Frequency estimation for single-carrier and OFDM signals in communication and radar systems
    (2009)
    Ubolkosold, Pakorn
    Estimating the frequency of a signal embedded in additive white Gaussian noise is one of the classical problems in signal processing. It is of fundamental importance in various applications such as in communications, Doppler radar, synthetic aperture radar (SAR), array processing, radio frequency identification (RFID), resonance sensor, etc. The requirement on the performance of the frequency estimator varies with the application. The performance is often defined using four indexes: i). estimation accuracy, ii). estimation range, iii). estimation threshold, and iv). implementation complexity. These indexes may be in contrast with each other. For example, achieving a low threshold usually implies a high complexity. Likewise, good estimation accuracy is often obtained at the price of a narrow estimation range. The estimation becomes even more difficult in the presence of fading-induced multiplicative noise which is considered to be the general case of the frequency estimation problem. There have been a lot of efforts in deriving the estimator for the general case, however, a generalized estimator that fulfills all indexes can be hardly obtained. Focusing on communications and radar applications, this thesis proposes a new generalized closed-form frequency estimator that compromises all performance indexes. The derivation of the proposed estimator relies on the nonlinear least-squares principle in conjunction with the well known summation-by-parts formula. In addition to this, several modified frequency estimators suitable for non-fading or very slow fading scenarios, are also introduced in this thesis.
    Source Type:Doctoral Thesis
      2  53