Institut für Informatik und Computational Science
Refine
Has Fulltext
- yes (244) (remove)
Year of publication
Document Type
- Article (116)
- Doctoral Thesis (84)
- Conference Proceeding (15)
- Master's Thesis (13)
- Postprint (10)
- Monograph/Edited Volume (2)
- Bachelor Thesis (1)
- Habilitation Thesis (1)
- Moving Images (1)
- Preprint (1)
Language
- English (125)
- German (118)
- Multiple languages (1)
Keywords
- Informatik (18)
- Didaktik (15)
- Hochschuldidaktik (14)
- Ausbildung (13)
- E-Learning (8)
- Maschinelles Lernen (7)
- Antwortmengenprogrammierung (6)
- Computer Science Education (5)
- Machine Learning (5)
- answer set programming (5)
- education (5)
- Informatikdidaktik (4)
- Modellierung (4)
- didactics (4)
- higher education (4)
- Answer Set Programming (3)
- Competence Measurement (3)
- DPLL (3)
- Digitalisierung (3)
- Komplexität (3)
- Ontologie (3)
- Secondary Education (3)
- Semantic Web (3)
- Softwareentwicklung (3)
- complexity (3)
- informatics (3)
- machine learning (3)
- Adaptivität (2)
- Algorithmen (2)
- Algorithms (2)
- Assessment (2)
- Autismus (2)
- Automatisches Beweisen (2)
- Big Data (2)
- Bildungstechnologien (2)
- Bildverarbeitung (2)
- Code (2)
- Competence Modelling (2)
- Computational thinking (2)
- Computer Science (2)
- Computergrafik (2)
- Computersicherheit (2)
- Constraint Solving (2)
- Data Privacy (2)
- Deduction (2)
- Digitale Medien (2)
- EEG (2)
- Educational Technologies (2)
- FMC (2)
- HCI (2)
- ICA (2)
- IT-Infrastruktur (2)
- Informatics (2)
- Informatics Education (2)
- Informatics Modelling (2)
- Informatics System Application (2)
- Informatics System Comprehension (2)
- Informatikstudium (2)
- Internet of Things (2)
- Key Competencies (2)
- Klausellernen (2)
- Knowledge Representation and Reasoning (2)
- Konstruktivismus (2)
- Künstliche Intelligenz (2)
- Lernumgebung (2)
- Logic Programming (2)
- Logics (2)
- MQTT (2)
- Mensch-Computer-Interaktion (2)
- Mensch-Technik-Interaktion (2)
- Methodik (2)
- Middleware (2)
- Modell (2)
- Onlinelehre (2)
- Ontology (2)
- Optimization (2)
- Planing (2)
- Prozessmodellierung (2)
- Relevanz (2)
- SAT (2)
- Software Engineering (2)
- Strategie (2)
- Systemstruktur (2)
- Texturen (2)
- Theorembeweisen (2)
- Unifikation (2)
- User Experience (2)
- Visualisierung (2)
- Vorhersage (2)
- abstraction (2)
- code (2)
- computational thinking (2)
- computer graphics (2)
- computer science education (2)
- human computer interaction (2)
- image processing (2)
- maschinelles Lernen (2)
- model (2)
- non-photorealistic rendering (2)
- relevance (2)
- scientific workflows (2)
- secondary computer science education (2)
- software development (2)
- systems biology (2)
- teacher training (2)
- test (2)
- textures (2)
- theorem (2)
- virtual 3D city models (2)
- virtuelle 3D-Stadtmodelle (2)
- visualization (2)
- 'Peer To Peer' (1)
- 13C metabolic flux analysis (1)
- 21st century skills, (1)
- 3D Computer Grafik (1)
- 3D Computer Graphics (1)
- 3D Drucken (1)
- 3D Linsen (1)
- 3D Semiotik (1)
- 3D Visualisierung (1)
- 3D computer graphics (1)
- 3D lenses (1)
- 3D printing (1)
- 3D semiotics (1)
- 3D visualization (1)
- 3D-Stadtmodelle (1)
- 3d city models (1)
- 6LoWPAN (1)
- ABRACADABRA (1)
- ADFS (1)
- ARCS Modell (1)
- ASIC (1)
- ASIC (Applikationsspezifische Integrierte Schaltkreise) (1)
- ASP (Answer Set Programming) (1)
- Abbrecherquote (1)
- Abstraktion (1)
- Accepting Grammars (1)
- Access Datenbank (1)
- Achievement (1)
- Ackerschmalwand (1)
- Active Directory Federation Services (1)
- Active Evaluation (1)
- Activity Theory (1)
- Activity-orientated Learning (1)
- Adaptivity (1)
- Adversarial Learning (1)
- Aktive Evaluierung (1)
- Akzeptierende Grammatiken (1)
- Algorithmenablaufplanung (1)
- Algorithmenkonfiguration (1)
- Algorithmenselektion (1)
- Alignment (1)
- Angewandte Spieltheorie (1)
- Anisotroper Kuwahara Filter (1)
- Anleitung (1)
- Antwortmengen Programmierung (1)
- Application Aggregation (1)
- Applications and Software Development (1)
- Applied Game Theory (1)
- Arabidopsis thaliana (1)
- Arduino (1)
- Argumentation (1)
- Artificial Intelligence (1)
- Aspect-Oriented Programming (1)
- Aspektorientierte Programmierung (1)
- Asynchrone Schaltung (1)
- Attention (1)
- Audience Response Systeme (1)
- Aufmerksamkeit (1)
- Aufzählung (1)
- Augenbewegungen (1)
- Ausreissererkennung (1)
- Austria (1)
- Authentifizierung (1)
- Authorization (1)
- Autism (1)
- Automated Theorem Proving (1)
- Automatic Item Generation (1)
- Automatic UI Generation (1)
- Autorisierung (1)
- BCH (1)
- BCH code (1)
- BCH-Code (1)
- BCI (1)
- BSS (1)
- Bachelorstudierende der Informatik (1)
- Baumweite (1)
- Behavior (1)
- Benutzeroberfläche (1)
- Benutzungsschnittstellen Ontologien (1)
- Berührungseingaben (1)
- Betrachtungsebenen (1)
- Beweis (1)
- Beweisassistent (1)
- Beweistheorie (1)
- Beweisumgebung (1)
- Bilddatenanalyse (1)
- Bildung (1)
- Binäres Entscheidungsdiagramm (1)
- Bio-jETI (1)
- Biocomputing (1)
- Bioelektrisches Signal (1)
- Bioinformatik (1)
- Blended Learning (1)
- Bloom’s Taxonomy (1)
- Boolean constraint solver (1)
- Boosting (1)
- Brain Computer Interface (1)
- Business Process Models (1)
- CASP (Constraint Answer Set Programming) (1)
- CS concepts (1)
- CSC (1)
- Cactus (1)
- Capability approach (1)
- Challenges (1)
- Choreographien (1)
- CityGML (1)
- Classification (1)
- Clause Learning (1)
- Cloud Computing (1)
- Cloud computing (1)
- Clusteranalyse (1)
- Codierung (1)
- Codierungstheorie (1)
- Coding theory (1)
- Cognitive Apprenticeship (1)
- Cognitive Skills (1)
- Common Spatial Pattern (1)
- Competences (1)
- Competencies (1)
- Complementary Circuits (1)
- Complexity (1)
- Compliance (1)
- Composed UIs (1)
- Composition (1)
- Computational Complexity (1)
- Computational Science (1)
- Computational Thinking (1)
- Computer Science in Context (1)
- Computergestützes Training (1)
- Computing (1)
- Conceptual (1)
- Constraint (1)
- Constraint-Programmierung (1)
- Constructive solid geometry (1)
- Contest (1)
- Contextualisation (1)
- Contradictions (1)
- Controlled Derivations (1)
- Coq (1)
- Covariate Shift (1)
- Curriculum (1)
- Curriculum Development (1)
- Curry (1)
- DDoS (1)
- DNA (1)
- DNA computing (1)
- DNS (1)
- Data Analysis (1)
- Data Management (1)
- Databases (1)
- Dateiformat (1)
- Datenschutz (1)
- Debugging (1)
- Deep Learning (1)
- Defining characteristics of physical computing (1)
- Dempster-Shafer-Theorie (1)
- Dempster–Shafer theory (1)
- Description Logics (1)
- Deskriptive Logik (1)
- Diagonalisierung (1)
- Dialog-based User Interfaces (1)
- Dialogbasierte Benutzerschnittstellen (1)
- Didaktik der Informatik (1)
- Didaktische Konzepte (1)
- Dienst-Ökosysteme (1)
- Dienstkomposition (1)
- Dienstplattform (1)
- Differenz von Gauss Filtern (1)
- Digital Competence (1)
- Digital Design (1)
- Digital Education (1)
- Digital Game Based Learning (1)
- Digital Media (1)
- Digital Revolution (1)
- Digitale Bibliothek (1)
- Digitalisation (1)
- Distributed Computing (1)
- Diversität (1)
- Dokument-Management-System (1)
- Domain-Specific Languages (1)
- Domänenspezifische Sprachen (1)
- Dreidimensionale Computergraphik (1)
- Dublin Core (1)
- Dynamic Programming (1)
- Dynamic assessment (1)
- Dynamische Programmierung (1)
- Dynamische Rekonfiguration (1)
- E-Assessment (1)
- E-Government (1)
- E-Klausuren (1)
- E-Portfolio (1)
- Early Literacy (1)
- Echtzeitanwendung (1)
- Educational Standards (1)
- Educational software (1)
- Eingabegenauigkeit (1)
- Eisenbahnnetz (1)
- Elektroencephalographie (1)
- Elektronisches Prüfen (1)
- Elektronisches Publizieren (1)
- Embedded Systems (1)
- Emotionen (1)
- Emotionsforschung (1)
- Enterprise Search (1)
- Entscheidungsbäume (1)
- Entwurf (1)
- Entwurfsmuster (1)
- Entwurfsmuster für SOA-Sicherheit (1)
- Entwurfsprinzipien (1)
- Entwurfsraumexploration (1)
- Equilibrium logic (1)
- Erfüllbarkeit einer Formel der Aussagenlogik (1)
- Erfüllbarkeitsproblem (1)
- Error Estimation (1)
- Error-Detection Circuits (1)
- Euclid’s algorithm (1)
- European Bioinformatics Institute (1)
- Evaluierung semantischer Suchmaschinen (1)
- Evidenztheorie (1)
- Exploration (1)
- Exponential Time Hypothesis (1)
- Exponentialzeit Hypothese (1)
- FMC-QE (1)
- FOSS (1)
- FPGA (1)
- Facebook (1)
- Feature Combination (1)
- Feedback (1)
- Fehlende Daten (1)
- Fehlererkennung (1)
- Fehlerkorrektur (1)
- Fehlerschätzung (1)
- Fehlvorstellung (1)
- Fibonacci numbers (1)
- Flussgesteuerter Bilateraler Filter (1)
- Focus+Context Visualization (1)
- Fokus-&-Kontext Visualisierung (1)
- Formalismus (1)
- Formalitätsgrad (1)
- Formeln der quantifizierten Aussagenlogik (1)
- Forschendes Lernen (1)
- Forschungsdatenmanagement (1)
- Function (1)
- Fundamental Ideas (1)
- GIS-Dienstkomposition (1)
- GPU (1)
- Game-Design-Elemente (1)
- Game-based learning (1)
- Gamification (1)
- Gebrauchstauglichkeit (1)
- Gebäudemodelle (1)
- Gehirn-Computer-Schnittstelle (1)
- Geländemodelle (1)
- Generalisierung (1)
- Generative Programmierung (1)
- Generative Programming (1)
- Geodaten (1)
- Geometrieerzeugung (1)
- Geovisualisierung (1)
- Geschäftsprozessmodelle (1)
- Gesichtsausdruck (1)
- Gesteuerte Ableitungen (1)
- Gleichheit (1)
- Globus (1)
- Grammar Systems (1)
- Grammatikalische Inferenz (1)
- Grammatiksysteme (1)
- Graph-basiertes Ranking (1)
- Graphensuche (1)
- Graphfärbung (1)
- Grid (1)
- Grid Computing (1)
- HDI (1)
- Hardware Design (1)
- Hardware-Software-Co-Design (1)
- Hauptkomponentenanalyse (1)
- Heterogenität (1)
- High-Level Synthesis (1)
- Hochschulbildung (1)
- Hochschullehre (1)
- Hochschulsystem (1)
- Human-Technology Interaction (1)
- I/O-effiziente Algorithmen (1)
- ICT (1)
- ICT Competence (1)
- ICT competencies (1)
- ICT skills (1)
- IP core (1)
- IT security (1)
- IT-Security (1)
- IT-Sicherheit (1)
- Informatik-Studiengänge (1)
- Informatiksystem (1)
- Informatikunterricht (1)
- Informatikvoraussetzungen (1)
- Information Retrieval (1)
- Information Transfer Rate (1)
- Informationsextraktion (1)
- Infrastruktur (1)
- Inkonsistenz (1)
- Innovation (1)
- Inquiry-based Learning (1)
- Inquiry-based learning (1)
- Integration (1)
- Interactive Rendering (1)
- Interactive system (1)
- Interaktionsmodel (1)
- Interaktionsmodellierung (1)
- Interaktionstechniken (1)
- Interaktives Rendering (1)
- Interaktives System (1)
- Interaktivität (1)
- Interface design (1)
- Internet Security (1)
- Internet applications (1)
- Internet-Sicherheit (1)
- Internetanwendungen (1)
- Interoperability (1)
- Interoperabilität (1)
- Intuition (1)
- IoT (1)
- Java Security Framework (1)
- Kartografisches Design (1)
- Kern-PCA (1)
- Kernmethoden (1)
- Klassifikation (1)
- Klassifikation mit großem Margin (1)
- Klassifikator-Kalibrierung (1)
- Klimafolgenanalyse (1)
- Klimawandel (1)
- Kommunikation (1)
- Kompetenz (1)
- Kompetenzerwerb (1)
- Komplexitätsbewältigung (1)
- Komplexitätstheorie (1)
- Komposition (1)
- Konnektionskalkül (1)
- Konzeptionell (1)
- Kryptographie (1)
- Kybernetik (1)
- LDPC code (1)
- LDPC-Code (1)
- LMS (1)
- Landmarken (1)
- Langzeitarchivierung (1)
- Large Margin Classification (1)
- Laser Cutten (1)
- Learners (1)
- Learning Analytics (1)
- Learning Fields (1)
- Learning ecology (1)
- Learning environment (1)
- Learning interfaces development (1)
- Learning with ICT (1)
- Lebenslanges Lernen (1)
- Leftmost Derivations (1)
- Lehrer (1)
- Lehrer*innenbildung (1)
- Lehrkräfteausbildung (1)
- Leistungsfähigkeit (1)
- Leistungsvorhersage (1)
- Lern-App (1)
- Lernaufgaben (1)
- Lernmotivation (1)
- Lernsoftware (1)
- Life-Long Learning (1)
- Liguistisch (1)
- Linked Data Anwendungen (1)
- Linked Data Application Modelling (1)
- Linksableitungen (1)
- Logarithm (1)
- Logik (1)
- Logikkalkül (1)
- Logiksynthese (1)
- Lower Bounds (1)
- Lower Secondary Level (1)
- MEG (1)
- MFA (1)
- MOOCs (1)
- Magnetoencephalographie (1)
- Malware (1)
- Massive Open Online Courses (1)
- Mathematical Optimization (1)
- Mathematikdidaktik (1)
- Mathematikphilosophie (1)
- Mathematische Optimierung (1)
- Matrizen-Eigenwertaufgabe (1)
- Measurement (1)
- Megamodel (1)
- Megamodell (1)
- Mehrklassen-Klassifikation (1)
- Message Passing Interface (1)
- Metamodell (1)
- Methoden der semantischen Suche (1)
- Methodology (1)
- Migration (1)
- Mischmodelle (1)
- Mischung <Signalverarbeitung> (1)
- Mobile App (1)
- Mobiles Lernen (1)
- Mobilgeräte (1)
- Model Based Engineering (1)
- Model Checking (1)
- Model Driven Architecture (1)
- Model Driven UI Development (1)
- Model Management (1)
- Model-Driven Engineering (1)
- Model-Driven Software Development (1)
- Modeling (1)
- Modell Management (1)
- Modell-driven Security (1)
- Modell-getriebene Sicherheit (1)
- Modellbasiert (1)
- Modellgetriebene Architektur (1)
- Modellgetriebene Entwicklung (1)
- Modellgetriebene Softwareentwicklung (1)
- Modellgetriebene UI Entwicklung (1)
- Modelling (1)
- Molekulare Bioinformatik (1)
- Motivation (1)
- Multi Task Learning (1)
- Multi-Class (1)
- Multi-Task-Lernen (1)
- Multimodal User Interfaces (1)
- Multimodale Benutzerschnittstellen (1)
- Multiprocessor (1)
- Multiprozessor (1)
- Music Technology (1)
- NETCONF (1)
- NUI (1)
- Natural Science Education (1)
- Navigation (1)
- Network Management (1)
- Netzwerk (1)
- Netzwerk Management (1)
- Netzwerke (1)
- Neuronales Netz (1)
- New On-Line Error-Detection Methode (1)
- Next Generation Network (1)
- Nicht-photorealistisches Rendering (1)
- Nichtfotorealistische Bildsynthese (1)
- NoSQL (1)
- Norway (1)
- Novice programmers (1)
- Nutzungserlebnis (1)
- Nutzungsinteresse (1)
- OAI-PMH (1)
- Objektive Schwierigkeit (1)
- Omega (1)
- Ontologien (1)
- Ontologies (1)
- Open Source (1)
- OpenOLAT (1)
- Optimierung (1)
- Optimierungsproblem (1)
- Owner-Retained Access Control (ORAC) (1)
- Parallel Programming (1)
- Parallele Datenverarbeitung (1)
- Paralleles Rechnen (1)
- Parallelrechner (1)
- Parameterized Complexity (1)
- Parametrisierte Komplexität (1)
- Parsing (1)
- Partizipation (1)
- Patterns (1)
- Pedagogical content knowledge (1)
- Peer-to-Peer-Netz ; GRID computing ; Zuverlässigkeit ; Web Services ; Betriebsmittelverwaltung ; Migration (1)
- Performance (1)
- Performance Prediction (1)
- Perl Formularskript (1)
- Persönliche Lernumgebung (1)
- Physical Science (1)
- Platzierung (1)
- Policy Enforcement (1)
- Policy Languages (1)
- Policy Sprachen (1)
- Power Monitoring (1)
- Pre-RS Traceability (1)
- Prediction Game (1)
- Predictive Models (1)
- Preprocessing (1)
- Problem Solving (1)
- Probleme in der Studie (1)
- Problemlösen (1)
- Process (1)
- Process modeling (1)
- Professoren (1)
- Programmierung (1)
- Proof Theory (1)
- Prototyp (1)
- Prototyping (1)
- Prozess (1)
- Prozess Verbesserung (1)
- Prozesse (1)
- Prozessmodell (1)
- Prozesssynchronisierung (1)
- Prädiktionsspiel (1)
- Präferenzen (1)
- Publikationsserver (1)
- Quantenkryptographie (1)
- Quantified Boolean Formula (QBF) (1)
- Quantitative Modeling (1)
- Quantitative Modellierung (1)
- Queuing Theory (1)
- Recommendations for CS-Curricula in Higher Education (1)
- Reconfigurable (1)
- Regression (1)
- Regularisierung (1)
- Regularization (1)
- Rekonfiguration (1)
- Rendering (1)
- Reparatur (1)
- Reuseable UIs (1)
- SMT (SAT Modulo Theories) (1)
- SOA Security Pattern (1)
- SSO (1)
- STG decomposition (1)
- STG-Dekomposition (1)
- Sample Selection Bias (1)
- Satisfiability (1)
- Scalability (1)
- Scene graph systems (1)
- Schlüsselkompetenzen (1)
- Schulmaterial (1)
- Security Modelling (1)
- Segmentierung (1)
- Selektion (1)
- Selektionsbias (1)
- Self-Checking Circuits (1)
- Semantic Search (1)
- Semantik Web (1)
- Semantische Suche (1)
- Sensornetzwerke (1)
- Sensors (1)
- Service Creation (1)
- Service Delivery Platform (1)
- Service Ecosystems (1)
- Service Oriented Architectures (1)
- Service convergence (1)
- Service-Orientierte Architekturen (1)
- Service-oriented Architectures (1)
- Serviceorientierte Architektur (1)
- Shader (1)
- Sicherheitsmodellierung (1)
- Signal Processing (1)
- Signalquellentrennung (1)
- Signaltrennung (1)
- Simultane Diagonalisierung (1)
- Single Event Transient (1)
- Single Sign On (1)
- Single Trial Analysis (1)
- Skalierbarkeit (1)
- Skelettberechnung (1)
- Small Private Online Courses (1)
- Social (1)
- Software (1)
- Software architecture (1)
- Software-basierte Cache-Kohärenz (1)
- Softwarearchitektur (1)
- Sonnenteilchen-Ereignis (1)
- Spam (1)
- Spam Filtering (1)
- Spam-Erkennung (1)
- Spam-Filter (1)
- Spam-Filtering (1)
- Spatio-Spectral Filter (1)
- Spawning (1)
- Spielbasiertes Lernen (1)
- Sprachdesign (1)
- Statistical Tests (1)
- Statistikprogramm R (1)
- Statistische Tests (1)
- Stilisierung (1)
- Strahlungshartes Design (1)
- Strahlungshärte Entwurf (1)
- Stromverbrauchüberwachung (1)
- Structuring (1)
- Strukturierung (1)
- Studentenerwartungen (1)
- Studentenhaltungen (1)
- Studentenjobs (1)
- Studienabbrecher (1)
- Studiendauer (1)
- Suche (1)
- Support Vectors (1)
- Support-Vector Lernen (1)
- Synthese (1)
- System Biologie (1)
- System structure (1)
- Systembiologie (1)
- Systementwurf (1)
- Szenengraph (1)
- TPTP (1)
- Tailored UI Variants (1)
- Taktik (1)
- Tasks (1)
- Teacher perceptions (1)
- Teachers (1)
- Teaching information security (1)
- Technology proficiency (1)
- Telekommunikation (1)
- Temporal Logic (1)
- Temporallogik (1)
- Temporäre Anbindung (1)
- Terminologische Logik (1)
- Terminology (1)
- Test (1)
- Tests (1)
- Theoretische Informatik (1)
- Theoretischen Vorlesungen (1)
- Theory (1)
- Time Augmented Petri Nets (1)
- Time Series Analysis (1)
- Tool (1)
- Traceability (1)
- Tracking (1)
- Transformation (1)
- Treewidth (1)
- UI Components (1)
- UI Metamodels (1)
- UI-Komponenten (1)
- Unabhängige Komponentenanalyse (1)
- Universität Bagdad (1)
- Universität Potsdam (1)
- Universitätseinstellungen (1)
- Untere Schranken (1)
- Unterrichtswerkzeuge (1)
- Unvollständigkeit (1)
- Usability (1)
- Usage Interest (1)
- User Interface Ontologies (1)
- User Interfaces (1)
- VM (1)
- Verhalten (1)
- Verifikation (1)
- Verletzung Auflösung (1)
- Verletzung Erklärung (1)
- Verteiltes Rechnen (1)
- Verteilungsunterschied (1)
- Violation Explanation (1)
- Violation Resolution (1)
- Virtual Reality (1)
- Virtuelles 3D Stadtmodell (1)
- Vocational Education (1)
- Vorhersagemodelle (1)
- Wahrnehmung (1)
- Wahrnehmung von Arousal (1)
- Wahrnehmungsunterschiede (1)
- Warteschlangentheorie (1)
- Web Services (1)
- Web Sites (1)
- Web of Data (1)
- Webseite (1)
- Weiterbildung (1)
- Well-structuredness (1)
- Wetterextreme (1)
- Wirtschaftsinformatik (1)
- Wissenschaftlichesworkflows (1)
- Wissensrepräsentation und -verarbeitung (1)
- Wissensrepräsentation und Schlussfolgerung (1)
- Wohlstrukturiertheit (1)
- Workflow (1)
- Young People (1)
- ZQSA (1)
- ZQSAT (1)
- Zeitbehaftete Petri Netze (1)
- Zero-Suppressed Binary Decision Diagram (ZDD) (1)
- Zuverlässigkeitsanalyse (1)
- adaptiv (1)
- adaptive (1)
- algorithm configuration (1)
- algorithm scheduling (1)
- algorithm selection (1)
- analogical thinking (1)
- animated PCA (1)
- animierte PCA (1)
- anisotropic Kuwahara filter (1)
- anti-cancer drugs (1)
- approximate joint diagonalization (1)
- argument mining (1)
- argumentation (1)
- argumentation structure (1)
- arithmethische Prozeduren (1)
- arithmetic procedures (1)
- arousal perception (1)
- artificial intelligence (1)
- assistive Technologien (1)
- assistive technologies (1)
- asynchronous circuit (1)
- authentication (1)
- automated theorem proving (1)
- automatic feedback (1)
- automatic theorem prover (1)
- automatisierter Theorembeweiser (1)
- bild (1)
- binary representation (1)
- binary search (1)
- bio-computing (1)
- biometrics (1)
- biometrische Identifikation (1)
- blind source separation (1)
- building models (1)
- business informatics (1)
- cartographic design (1)
- changing the study field (1)
- changing the university (1)
- choreographies (1)
- classifier calibration (1)
- classroom language (1)
- classroom material (1)
- clause learning (1)
- climate change (1)
- climate impact analysis (1)
- clustering (1)
- cognitive apprenticeship (1)
- cognitive modifiability (1)
- coherence-enhancing filtering (1)
- communication (1)
- competence (1)
- competencies (1)
- competency (1)
- comprehension (1)
- computational biology (1)
- computational methods (1)
- computer science teachers (1)
- computer security (1)
- computergestützte Methoden (1)
- concurrent checking (1)
- connection calculus (1)
- constraint (1)
- constraint programming (1)
- constraints (1)
- constructivism (1)
- construktivism (1)
- cryptography (1)
- cs4fn (1)
- curriculum theory (1)
- debugging (1)
- decision trees (1)
- deep neural networks (1)
- degree of formality (1)
- design (1)
- design principles (1)
- design space exploration (1)
- didaktische Rekonstruktion (1)
- didaktisches Konzept (1)
- difference of Gaussians (1)
- digital circuit (1)
- digital design (1)
- digitale Bildung (1)
- digitale Hochschullehre (1)
- digitale Medien (1)
- digitally-enabled pedagogies (1)
- divide and conquer (1)
- dropout (1)
- drug-sensitivity prediction (1)
- dynamic (1)
- dynamic classification (1)
- dynamic reconfiguration (1)
- dynamisch (1)
- dynamische Klassifikation (1)
- e-Learning (1)
- e-mentoring (1)
- eGovernment (1)
- edge computing (1)
- education and public policy (1)
- educational programming (1)
- educational reconstruction (1)
- educational systems (1)
- edutainment (1)
- eingebettete Systeme (1)
- einseitige Kommunikation (1)
- email spam detection (1)
- embedded systems (1)
- emotion (1)
- emotion representation (1)
- emotion research (1)
- enterprise search (1)
- entity alignment (1)
- enumeration (1)
- environments (1)
- epistemic logic programs (1)
- epistemic specifications (1)
- equality (1)
- error correction (1)
- error detection (1)
- evidence theory (1)
- explicit negation (1)
- exponentiation (1)
- external memory algorithms (1)
- eye movements (1)
- face tracking (1)
- facial expression (1)
- firmware update (1)
- flow-based bilateral filter (1)
- formalism (1)
- freie Daten (1)
- freie Software (1)
- fun (1)
- game based learning (1)
- game design elements (1)
- game-based learning (1)
- generalization (1)
- geometry generation (1)
- geospatial data (1)
- geospatial services (1)
- geovisualization (1)
- global constraints (1)
- globale Constraints (1)
- grammar inference (1)
- graph clustering (1)
- graph-based ranking (1)
- graph-search (1)
- hardware design (1)
- hardware-software-codesign (1)
- high school (1)
- high-throughput analysis (1)
- higher (1)
- human-technology interaction (1)
- hybrid (1)
- hybrid semantic search (1)
- hybride semantische Suche (1)
- hybrides Problemlösen (1)
- image (1)
- image data analysis (1)
- incompleteness (1)
- inconsistency (1)
- independent component analysis (1)
- indirect economic impacts (1)
- indirekte ökonomische Effekte (1)
- informal and formal learning (1)
- informatics education (1)
- information extraction (1)
- information retrieval (1)
- informatische Bildung im Sekundarbereich (1)
- infrastructure (1)
- innovation (1)
- input accuracy (1)
- interaction modeling (1)
- interaction techniques (1)
- interactive course (1)
- interactive workshop (1)
- intuition (1)
- kernel PCA (1)
- kernel methods (1)
- key competences in physical computing (1)
- key competencies (1)
- kinaesthetic teaching (1)
- klinisch-praktischer Unterricht (1)
- konvergente Dienste (1)
- landmarks (1)
- language design (1)
- lautes Denken (1)
- leanCoP (1)
- learning (1)
- learning environment (1)
- lebenslanges Lernen (1)
- lesson planning (1)
- lesson preparation (1)
- linear code (1)
- linearer Code (1)
- linguistic (1)
- logic (1)
- logic programming (1)
- logic synthesis (1)
- logical calculus (1)
- logical errors (1)
- logical signaling networks (1)
- logische Ergänzung (1)
- logische Fehler (1)
- logische Programmierung (1)
- logische Signalnetzwerke (1)
- macro-economic modelling (1)
- makroökonomische Modellierung (1)
- malware detection (1)
- map/reduce (1)
- maschninelles Lernen (1)
- mathematics education (1)
- mediated learning experience (1)
- medical (1)
- medizinisch (1)
- meta model (1)
- methodology (1)
- middleware (1)
- misconception (1)
- mixture models (1)
- mobile devices (1)
- mobile learning (1)
- mobile technologies and apps (1)
- mobiles Lernen (1)
- mobiles lernen (1)
- model-based (1)
- model-driven architecture (1)
- modeling (1)
- molecular networks (1)
- molekulare Netzwerke (1)
- multi core data processing (1)
- multi-class classification (1)
- multiuser (1)
- navigation (1)
- network (1)
- networks (1)
- networks-on-chip (1)
- neue Online-Fehlererkennungsmethode (1)
- nichtlineare ICA (1)
- nichtlineare PCA (NLPCA) (1)
- nichtlineare Projektionen (1)
- non-monotonic reasoning (1)
- nonlinear ICA (1)
- nonlinear PCA (NLPCA) (1)
- nonlinear projections (1)
- objective difficulty (1)
- omega (1)
- on-chip (1)
- one-sided communication (1)
- oneM2M (1)
- online assistance (1)
- ontologies (1)
- open learning (1)
- open source (1)
- operating system (1)
- optimization (1)
- organisational evolution (1)
- outlier detection (1)
- output space compaction (1)
- overcomplete ICA (1)
- paper prototyping (1)
- parallel programming (1)
- parallel solving (1)
- parallele Programmierung (1)
- paralleles Lösen (1)
- parameter (1)
- parsing (1)
- pattern recognition (1)
- pedagogy (1)
- perception (1)
- perception differences (1)
- personal (1)
- personal response systems (1)
- philosophical foundation of informatics pedagogy (1)
- philosophy of mathematics (1)
- physical Computing (1)
- physical computing (1)
- physical computing tools (1)
- placement (1)
- policy evaluation (1)
- pre-primary level (1)
- prediction (1)
- preferences (1)
- preprocessing (1)
- primary education (1)
- primary level (1)
- priorities (1)
- probabilistic deep learning (1)
- probabilistic deep metric learning (1)
- probabilistische tiefe neuronale Netze (1)
- probabilistisches tiefes metrisches Lernen (1)
- problem-solving (1)
- process (1)
- process improvement (1)
- process model (1)
- process modelling (1)
- process synchronization (1)
- professional development (1)
- professors (1)
- programming (1)
- programming in context (1)
- proof (1)
- proof assistant (1)
- proof environment (1)
- propagation probability (1)
- prototype (1)
- proving (1)
- quantum cryptography (1)
- radiation hardness (1)
- radiation hardness design (1)
- railway network (1)
- real-time application (1)
- reconfiguration (1)
- rekonfigurierbar (1)
- reliability assessment (1)
- repair (1)
- robust ICA (1)
- robuste ICA (1)
- scheduling (1)
- search (1)
- secondary education (1)
- security (1)
- segmentation (1)
- selbstanpassendes Multiprozessorsystem (1)
- selbstprüfende Schaltungen (1)
- selection (1)
- self-adaptive multiprocessing system (1)
- self-efficacy (1)
- semantic domain modeling (1)
- semantic ranking (1)
- semantic search (1)
- semantic search evaluation (1)
- semantic search methods (1)
- semantische Domänenmodellierung (1)
- semantische Suche (1)
- semantisches Netz (1)
- semantisches Ranking (1)
- service composition (1)
- shader (1)
- sign language (1)
- single event upset (1)
- skeletonization (1)
- social media (1)
- socio-technical system (1)
- software (1)
- software engineering (1)
- software-based cache coherence (1)
- solar particle event (1)
- sozio-technisches System (1)
- speed independence (1)
- statistics program R (1)
- strahleninduzierte Einzelereignis-Effekte (1)
- structured output prediction (1)
- strukturierte Vorhersage (1)
- student activation (1)
- student experience (1)
- student perceptions (1)
- students’ conceptions (1)
- students’ knowledge (1)
- study problems (1)
- stylization (1)
- support system (1)
- systematic (1)
- systematisch (1)
- tactic (1)
- teacher competencies (1)
- teachers (1)
- teaching informatics in general education (1)
- technische Rahmenbedingungen (1)
- temporary binding (1)
- terrain models (1)
- think aloud (1)
- tools (1)
- tools for teaching (1)
- topics (1)
- touch input (1)
- tptp (1)
- tracing (1)
- transformation (1)
- tutorial section (1)
- unification (1)
- university education (1)
- user interfaces (1)
- user-centred (1)
- verification (1)
- virtual 3D city model (1)
- virtual machine (1)
- virtual mobility (1)
- virtual reality (1)
- weather extremes (1)
- workflow management (1)
- zero-aliasing (1)
- überbestimmte ICA (1)
- ‘unplugged’ computing (1)
Institute
- Institut für Informatik und Computational Science (244)
- Hasso-Plattner-Institut für Digital Engineering gGmbH (18)
- Extern (6)
- eLiS - E-Learning in Studienbereichen (2)
- Historisches Institut (1)
- Potsdam Institute for Climate Impact Research (PIK) e. V. (1)
- Universitätsbibliothek (1)
- Wirtschaftswissenschaften (1)
- Zentrum für Qualitätsentwicklung in Lehre und Studium (ZfQ) (1)
In einigen Bereichen der Informatiklehre ist es möglich, die persönlichen Erfahrungen der Studierenden im Umgang mit Informationstechnik aufzugreifen und vor dem Hintergrund theoretischer Konzepte aus der Literatur gemeinsam mit ihnen zu reflektieren. Das hier vorgestellte Lehrkonzept des Reflexionsdialogs erstreckt sich über drei Seminartermine und vorbereitende Selbstlernphasen. Unterstützt wird das Konzept durch DialogueMaps, eine Software zur Visualisierung komplexer Sachverhalte und zur Unterstützung interaktiver Dialoge. Dieser Beitrag beschreibt die Hintergründe des Lehrkonzeptes, das Lehrkonzept selbst sowie die inhaltliche Ausgestaltung im Rahmen eines Mastermoduls „Computergestützte Kooperation“.
Deciphering the functioning of biological networks is one of the central tasks in systems biology. In particular, signal transduction networks are crucial for the understanding of the cellular response to external and internal perturbations. Importantly, in order to cope with the complexity of these networks, mathematical and computational modeling is required. We propose a computational modeling framework in order to achieve more robust discoveries in the context of logical signaling networks. More precisely, we focus on modeling the response of logical signaling networks by means of automated reasoning using Answer Set Programming (ASP). ASP provides a declarative language for modeling various knowledge representation and reasoning problems. Moreover, available ASP solvers provide several reasoning modes for assessing the multitude of answer sets. Therefore, leveraging its rich modeling language and its highly efficient solving capacities, we use ASP to address three challenging problems in the context of logical signaling networks: learning of (Boolean) logical networks, experimental design, and identification of intervention strategies. Overall, the contribution of this thesis is three-fold. Firstly, we introduce a mathematical framework for characterizing and reasoning on the response of logical signaling networks. Secondly, we contribute to a growing list of successful applications of ASP in systems biology. Thirdly, we present a software providing a complete pipeline for automated reasoning on the response of logical signaling networks.
An increasing number of applications requires user interfaces that facilitate the handling of large geodata sets. Using virtual 3D city models, complex geospatial information can be communicated visually in an intuitive way. Therefore, real-time visualization of virtual 3D city models represents a key functionality for interactive exploration, presentation, analysis, and manipulation of geospatial data. This thesis concentrates on the development and implementation of concepts and techniques for real-time city model visualization. It discusses rendering algorithms as well as complementary modeling concepts and interaction techniques. Particularly, the work introduces a new real-time rendering technique to handle city models of high complexity concerning texture size and number of textures. Such models are difficult to handle by current technology, primarily due to two problems: - Limited texture memory: The amount of simultaneously usable texture data is limited by the memory of the graphics hardware. - Limited number of textures: Using several thousand different textures simultaneously causes significant performance problems due to texture switch operations during rendering. The multiresolution texture atlases approach, introduced in this thesis, overcomes both problems. During rendering, it permanently maintains a small set of textures that are sufficient for the current view and the screen resolution available. The efficiency of multiresolution texture atlases is evaluated in performance tests. To summarize, the results demonstrate that the following goals have been achieved: - Real-time rendering becomes possible for 3D scenes whose amount of texture data exceeds the main memory capacity. - Overhead due to texture switches is kept permanently low, so that the number of different textures has no significant effect on the rendering frame rate. Furthermore, this thesis introduces two new approaches for real-time city model visualization that use textures as core visualization elements: - An approach for visualization of thematic information. - An approach for illustrative visualization of 3D city models. Both techniques demonstrate that multiresolution texture atlases provide a basic functionality for the development of new applications and systems in the domain of city model visualization.
In der Lehre zur MCI (Mensch-Computer-Interaktion) stellt sich immer wieder die Herausforderung, praktische Übungen mit spannenden Ergebnissen durchzuführen, die sich dennoch nicht in technischen Details verlieren sondern MCI-fokussiert bleiben. Im Lehrmodul „Interaktionsdesign“ an der Universität Hamburg werden von Studierenden innerhalb von drei Wochen prototypische Interaktionskonzepte für das Spiel Neverball entworfen und praktisch umgesetzt. Anders als in den meisten Grundlagenkursen zur MCI werden hier nicht Mock-Ups, sondern lauffähige Software entwickelt. Um dies innerhalb der Projektzeit zu ermöglichen, wurde Neverball um eine TCP-basierte Schnittstelle erweitert. So entfällt die aufwändige Einarbeitung in den Quellcode des Spiels und die Studierenden können sich auf ihre Interaktionsprototypen konzentrieren. Wir beschreiben die Erfahrungen aus der
mehrmaligen Durchführung des Projektes und erläutern unser Vorgehen bei der Umsetzung. Die Ergebnisse sollen Lehrende im Bereich MCI unterstützen, ähnliche praxisorientierte Übungen mit Ergebnissen „zum Anfassen“ zu gestalten.
Three quantum cryptographic protocols of multiuser quantum networks with embedded authentication, allowing quantum key distribution or quantum direct communication, are discussed in this work. The security of the protocols against different types of attacks is analysed with a focus on various impersonation attacks and the man-in-the-middle attack. On the basis of the security analyses several improvements are suggested and implemented in order to adjust the investigated vulnerabilities. Furthermore, the impact of the eavesdropping test procedure on impersonation attacks is outlined. The framework of a general eavesdropping test is proposed to provide additional protection against security risks in impersonation attacks.
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.
Pseudo
(2010)
Pseudo ist eine auf Pseudocode basierende Programmiersprache, welche in der akademischen Lehre zum Einsatz kommen und hier die Vermittlung und Untersuchung von Algorithmen und Datenstrukturen unterstützen soll. Dieser Beitrag geht auf die Besonderheiten der Sprache sowie mögliche didaktische Szenarien ein.
ProtoSense
(2015)
Answer Set Programming (ASP) is an emerging paradigm for declarative programming, in which a computational problem is specified by a logic program such that particular models, called answer sets, match solutions. ASP faces a growing range of applications, demanding for high-performance tools able to solve complex problems. ASP integrates ideas from a variety of neighboring fields. In particular, automated techniques to search for answer sets are inspired by Boolean Satisfiability (SAT) solving approaches. While the latter have firm proof-theoretic foundations, ASP lacks formal frameworks for characterizing and comparing solving methods. Furthermore, sophisticated search patterns of modern SAT solvers, successfully applied in areas like, e.g., model checking and verification, are not yet established in ASP solving. We address these deficiencies by, for one, providing proof-theoretic frameworks that allow for characterizing, comparing, and analyzing approaches to answer set computation. For another, we devise modern ASP solving algorithms that integrate and extend state-of-the-art techniques for Boolean constraint solving. We thus contribute to the understanding of existing ASP solving approaches and their interconnections as well as to their enhancement by incorporating sophisticated search patterns. The central idea of our approach is to identify atomic as well as composite constituents of a propositional logic program with Boolean variables. This enables us to describe fundamental inference steps, and to selectively combine them in proof-theoretic characterizations of various ASP solving methods. In particular, we show that different concepts of case analyses applied by existing ASP solvers implicate mutual exponential separations regarding their best-case complexities. We also develop a generic proof-theoretic framework amenable to language extensions, and we point out that exponential separations can likewise be obtained due to case analyses on them. We further exploit fundamental inference steps to derive Boolean constraints characterizing answer sets. They enable the conception of ASP solving algorithms including search patterns of modern SAT solvers, while also allowing for direct technology transfers between the areas of ASP and SAT solving. Beyond the search for one answer set of a logic program, we address the enumeration of answer sets and their projections to a subvocabulary, respectively. The algorithms we develop enable repetition-free enumeration in polynomial space without being intrusive, i.e., they do not necessitate any modifications of computations before an answer set is found. Our approach to ASP solving is implemented in clasp, a state-of-the-art Boolean constraint solver that has successfully participated in recent solver competitions. Although we do here not address the implementation techniques of clasp or all of its features, we present the principles of its success in the context of ASP solving.
Ziel einer neuen Studieneingangsphase ist, den Studierenden bis zum Ende des ersten Semesters ein vielfältiges Berufsbild der Informatik und Wirtschaftsinformatik mit dem breiten Aufgabenspektrum aufzublättern und damit die Zusammenhänge zwischen den einzelnen Modulen des Curriculums zu verdeutlichen. Die Studierenden sollen in die Lage versetzt werden, sehr eigenständig die Planung und Gestaltung ihres Studiums in die Hand zu nehmen.
The study reported in this paper involved the employment
of specific in-class exercises using a Personal Response System (PRS).
These exercises were designed with two goals: to enhance students’
capabilities of tracing a given code and of explaining a given code in
natural language with some abstraction. The paper presents evidence
from the actual use of the PRS along with students’ subjective impressions
regarding both the use of the PRS and the special exercises. The
conclusions from the findings are followed with a short discussion on
benefits of PRS-based mental processing exercises for learning programming
and beyond.
The workshops on (constraint) logic programming (WLP) are the annual meeting of the Society of Logic Programming (GLP e.V.) and bring together researchers interested in logic programming, constraint programming, and related areas like databases, artificial intelligence and operations research. The 23rd WLP was held in Potsdam at September 15 – 16, 2009. The topics of the presentations of WLP2009 were grouped into the major areas: Databases, Answer Set Programming, Theory and Practice of Logic Programming as well as Constraints and Constraint Handling Rules.
A central insight from psychological studies on human eye movements is that eye movement patterns are highly individually characteristic. They can, therefore, be used as a biometric feature, that is, subjects can be identified based on their eye movements. This thesis introduces new machine learning methods to identify subjects based on their eye movements while viewing arbitrary content. The thesis focuses on probabilistic modeling of the problem, which has yielded the best results in the most recent literature. The thesis studies the problem in three phases by proposing a purely probabilistic, probabilistic deep learning, and probabilistic deep metric learning approach. In the first phase, the thesis studies models that rely on psychological concepts about eye movements. Recent literature illustrates that individual-specific distributions of gaze patterns can be used to accurately identify individuals. In these studies, models were based on a simple parametric family of distributions. Such simple parametric models can be robustly estimated from sparse data, but have limited flexibility to capture the differences between individuals. Therefore, this thesis proposes a semiparametric model of gaze patterns that is flexible yet robust for individual identification. These patterns can be understood as domain knowledge derived from psychological literature. Fixations and saccades are examples of simple gaze patterns. The proposed semiparametric densities are drawn under a Gaussian process prior centered at a simple parametric distribution. Thus, the model will stay close to the parametric class of densities if little data is available, but it can also deviate from this class if enough data is available, increasing the flexibility of the model. The proposed method is evaluated on a large-scale dataset, showing significant improvements over the state-of-the-art. Later, the thesis replaces the model based on gaze patterns derived from psychological concepts with a deep neural network that can learn more informative and complex patterns from raw eye movement data. As previous work has shown that the distribution of these patterns across a sequence is informative, a novel statistical aggregation layer called the quantile layer is introduced. It explicitly fits the distribution of deep patterns learned directly from the raw eye movement data. The proposed deep learning approach is end-to-end learnable, such that the deep model learns to extract informative, short local patterns while the quantile layer learns to approximate the distributions of these patterns. Quantile layers are a generic approach that can converge to standard pooling layers or have a more detailed description of the features being pooled, depending on the problem. The proposed model is evaluated in a large-scale study using the eye movements of subjects viewing arbitrary visual input. The model improves upon the standard pooling layers and other statistical aggregation layers proposed in the literature. It also improves upon the state-of-the-art eye movement biometrics by a wide margin. Finally, for the model to identify any subject — not just the set of subjects it is trained on — a metric learning approach is developed. Metric learning learns a distance function over instances. The metric learning model maps the instances into a metric space, where sequences of the same individual are close, and sequences of different individuals are further apart. This thesis introduces a deep metric learning approach with distributional embeddings. The approach represents sequences as a set of continuous distributions in a metric space; to achieve this, a new loss function based on Wasserstein distances is introduced. The proposed method is evaluated on multiple domains besides eye movement biometrics. This approach outperforms the state of the art in deep metric learning in several domains while also outperforming the state of the art in eye movement biometrics.
This thesis proposes a privacy protection framework for the controlled distribution and use of personal private data. The framework is based on the idea that privacy policies can be set directly by the data owner and can be automatically enforced against the data user. Data privacy continues to be a very important topic, as our dependency on electronic communication maintains its current growth, and private data is shared between multiple devices, users and locations. The growing amount and the ubiquitous availability of personal private data increases the likelihood of data misuse. Early privacy protection techniques, such as anonymous email and payment systems have focused on data avoidance and anonymous use of services. They did not take into account that data sharing cannot be avoided when people participate in electronic communication scenarios that involve social interactions. This leads to a situation where data is shared widely and uncontrollably and in most cases the data owner has no control over further distribution and use of personal private data. Previous efforts to integrate privacy awareness into data processing workflows have focused on the extension of existing access control frameworks with privacy aware functions or have analysed specific individual problems such as the expressiveness of policy languages. So far, very few implementations of integrated privacy protection mechanisms exist and can be studied to prove their effectiveness for privacy protection. Second level issues that stem from practical application of the implemented mechanisms, such as usability, life-time data management and changes in trustworthiness have received very little attention so far, mainly because they require actual implementations to be studied. Most existing privacy protection schemes silently assume that it is the privilege of the data user to define the contract under which personal private data is released. Such an approach simplifies policy management and policy enforcement for the data user, but leaves the data owner with a binary decision to submit or withhold his or her personal data based on the provided policy. We wanted to empower the data owner to express his or her privacy preferences through privacy policies that follow the so-called Owner-Retained Access Control (ORAC) model. ORAC has been proposed by McCollum, et al. as an alternate access control mechanism that leaves the authority over access decisions by the originator of the data. The data owner is given control over the release policy for his or her personal data, and he or she can set permissions or restrictions according to individually perceived trust values. Such a policy needs to be expressed in a coherent way and must allow the deterministic policy evaluation by different entities. The privacy policy also needs to be communicated from the data owner to the data user, so that it can be enforced. Data and policy are stored together as a Protected Data Object that follows the Sticky Policy paradigm as defined by Mont, et al. and others. We developed a unique policy combination approach that takes usability aspects for the creation and maintenance of policies into consideration. Our privacy policy consists of three parts: A Default Policy provides basic privacy protection if no specific rules have been entered by the data owner. An Owner Policy part allows the customisation of the default policy by the data owner. And a so-called Safety Policy guarantees that the data owner cannot specify disadvantageous policies, which, for example, exclude him or her from further access to the private data. The combined evaluation of these three policy-parts yields the necessary access decision. The automatic enforcement of privacy policies in our protection framework is supported by a reference monitor implementation. We started our work with the development of a client-side protection mechanism that allows the enforcement of data-use restrictions after private data has been released to the data user. The client-side enforcement component for data-use policies is based on a modified Java Security Framework. Privacy policies are translated into corresponding Java permissions that can be automatically enforced by the Java Security Manager. When we later extended our work to implement server-side protection mechanisms, we found several drawbacks for the privacy enforcement through the Java Security Framework. We solved this problem by extending our reference monitor design to use Aspect-Oriented Programming (AOP) and the Java Reflection API to intercept data accesses in existing applications and provide a way to enforce data owner-defined privacy policies for business applications.
Answer Set Programming (ASP) emerged in the late 1990s as a new logic programming paradigm, having its roots in nonmonotonic reasoning, deductive databases, and logic programming with negation as failure. The basic idea of ASP is to represent a computational problem as a logic program whose answer sets correspond to solutions, and then to use an answer set solver for finding answer sets of the program. ASP is particularly suited for solving NP-complete search problems. Among these, we find applications to product configuration, diagnosis, and graph-theoretical problems, e.g. finding Hamiltonian cycles. On different lines of ASP research, many extensions of the basic formalism have been proposed. The most intensively studied one is the modelling of preferences in ASP. They constitute a natural and effective way of selecting preferred solutions among a plethora of solutions for a problem. For example, preferences have been successfully used for timetabling, auctioning, and product configuration. In this thesis, we concentrate on preferences within answer set programming. Among several formalisms and semantics for preference handling in ASP, we concentrate on ordered logic programs with the underlying D-, W-, and B-semantics. In this setting, preferences are defined among rules of a logic program. They select preferred answer sets among (standard) answer sets of the underlying logic program. Up to now, those preferred answer sets have been computed either via a compilation method or by meta-interpretation. Hence, the question comes up, whether and how preferences can be integrated into an existing ASP solver. To solve this question, we develop an operational graph-based framework for the computation of answer sets of logic programs. Then, we integrate preferences into this operational approach. We empirically observe that our integrative approach performs in most cases better than the compilation method or meta-interpretation. Another research issue in ASP are optimization methods that remove redundancies, as also found in database query optimizers. For these purposes, the rather recently suggested notion of strong equivalence for ASP can be used. If a program is strongly equivalent to a subprogram of itself, then one can always use the subprogram instead of the original program, a technique which serves as an effective optimization method. Up to now, strong equivalence has not been considered for logic programs with preferences. In this thesis, we tackle this issue and generalize the notion of strong equivalence to ordered logic programs. We give necessary and sufficient conditions for the strong equivalence of two ordered logic programs. Furthermore, we provide program transformations for ordered logic programs and show in how far preferences can be simplified. Finally, we present two new applications for preferences within answer set programming. First, we define new procedures for group decision making, which we apply to the problem of scheduling a group meeting. As a second new application, we reconstruct a linguistic problem appearing in German dialects within ASP. Regarding linguistic studies, there is an ongoing debate about how unique the rule systems of language are in human cognition. The reconstruction of grammatical regularities with tools from computer science has consequences for this debate: if grammars can be modelled this way, then they share core properties with other non-linguistic rule systems.
Preface
(2010)
The workshops on (constraint) logic programming (WLP) are the annual meeting of the Society of Logic Programming (GLP e.V.) and bring together researchers interested in logic programming, constraint programming, and related areas like databases, artificial intelligence and operations research. In this decade, previous workshops took place in Dresden (2008), Würzburg (2007), Vienna (2006), Ulm (2005), Potsdam (2004), Dresden (2002), Kiel (2001), and Würzburg (2000). Contributions to workshops deal with all theoretical, experimental, and application aspects of constraint programming (CP) and logic programming (LP), including foundations of constraint/ logic programming. Some of the special topics are constraint solving and optimization, extensions of functional logic programming, deductive databases, data mining, nonmonotonic reasoning, , interaction of CP/LP with other formalisms like agents, XML, JAVA, program analysis, program transformation, program verification, meta programming, parallelism and concurrency, answer set programming, implementation and software techniques (e.g., types, modularity, design patterns), applications (e.g., in production, environment, education, internet), constraint/logic programming for semantic web systems and applications, reasoning on the semantic web, data modelling for the web, semistructured data, and web query languages.
Learning a model for the relationship between the attributes and the annotated labels of data examples serves two purposes. Firstly, it enables the prediction of the label for examples without annotation. Secondly, the parameters of the model can provide useful insights into the structure of the data. If the data has an inherent partitioned structure, it is natural to mirror this structure in the model. Such mixture models predict by combining the individual predictions generated by the mixture components which correspond to the partitions in the data. Often the partitioned structure is latent, and has to be inferred when learning the mixture model. Directly evaluating the accuracy of the inferred partition structure is, in many cases, impossible because the ground truth cannot be obtained for comparison. However it can be assessed indirectly by measuring the prediction accuracy of the mixture model that arises from it. This thesis addresses the interplay between the improvement of predictive accuracy by uncovering latent cluster structure in data, and further addresses the validation of the estimated structure by measuring the accuracy of the resulting predictive model. In the application of filtering unsolicited emails, the emails in the training set are latently clustered into advertisement campaigns. Uncovering this latent structure allows filtering of future emails with very low false positive rates. In order to model the cluster structure, a Bayesian clustering model for dependent binary features is developed in this thesis. Knowing the clustering of emails into campaigns can also aid in uncovering which emails have been sent on behalf of the same network of captured hosts, so-called botnets. This association of emails to networks is another layer of latent clustering. Uncovering this latent structure allows service providers to further increase the accuracy of email filtering and to effectively defend against distributed denial-of-service attacks. To this end, a discriminative clustering model is derived in this thesis that is based on the graph of observed emails. The partitionings inferred using this model are evaluated through their capacity to predict the campaigns of new emails. Furthermore, when classifying the content of emails, statistical information about the sending server can be valuable. Learning a model that is able to make use of it requires training data that includes server statistics. In order to also use training data where the server statistics are missing, a model that is a mixture over potentially all substitutions thereof is developed. Another application is to predict the navigation behavior of the users of a website. Here, there is no a priori partitioning of the users into clusters, but to understand different usage scenarios and design different layouts for them, imposing a partitioning is necessary. The presented approach simultaneously optimizes the discriminative as well as the predictive power of the clusters. Each model is evaluated on real-world data and compared to baseline methods. The results show that explicitly modeling the assumptions about the latent cluster structure leads to improved predictions compared to the baselines. It is beneficial to incorporate a small number of hyperparameters that can be tuned to yield the best predictions in cases where the prediction accuracy can not be optimized directly.
In many applications one is faced with the problem of inferring some functional relation between input and output variables from given data. Consider, for instance, the task of email spam filtering where one seeks to find a model which automatically assigns new, previously unseen emails to class spam or non-spam. Building such a predictive model based on observed training inputs (e.g., emails) with corresponding outputs (e.g., spam labels) is a major goal of machine learning. Many learning methods assume that these training data are governed by the same distribution as the test data which the predictive model will be exposed to at application time. That assumption is violated when the test data are generated in response to the presence of a predictive model. This becomes apparent, for instance, in the above example of email spam filtering. Here, email service providers employ spam filters and spam senders engineer campaign templates such as to achieve a high rate of successful deliveries despite any filters. Most of the existing work casts such situations as learning robust models which are unsusceptible against small changes of the data generation process. The models are constructed under the worst-case assumption that these changes are performed such to produce the highest possible adverse effect on the performance of the predictive model. However, this approach is not capable to realistically model the true dependency between the model-building process and the process of generating future data. We therefore establish the concept of prediction games: We model the interaction between a learner, who builds the predictive model, and a data generator, who controls the process of data generation, as an one-shot game. The game-theoretic framework enables us to explicitly model the players' interests, their possible actions, their level of knowledge about each other, and the order at which they decide for an action. We model the players' interests as minimizing their own cost function which both depend on both players' actions. The learner's action is to choose the model parameters and the data generator's action is to perturbate the training data which reflects the modification of the data generation process with respect to the past data. We extensively study three instances of prediction games which differ regarding the order in which the players decide for their action. We first assume that both player choose their actions simultaneously, that is, without the knowledge of their opponent's decision. We identify conditions under which this Nash prediction game has a meaningful solution, that is, a unique Nash equilibrium, and derive algorithms that find the equilibrial prediction model. As a second case, we consider a data generator who is potentially fully informed about the move of the learner. This setting establishes a Stackelberg competition. We derive a relaxed optimization criterion to determine the solution of this game and show that this Stackelberg prediction game generalizes existing prediction models. Finally, we study the setting where the learner observes the data generator's action, that is, the (unlabeled) test data, before building the predictive model. As the test data and the training data may be governed by differing probability distributions, this scenario reduces to learning under covariate shift. We derive a new integrated as well as a two-stage method to account for this data set shift. In case studies on email spam filtering we empirically explore properties of all derived models as well as several existing baseline methods. We show that spam filters resulting from the Nash prediction game as well as the Stackelberg prediction game in the majority of cases outperform other existing baseline methods.
Large-scale databases that report the inhibitory capacities of many combinations of candidate drug compounds and cultivated cancer cell lines have driven the development of preclinical drug-sensitivity models based on machine learning. However, cultivated cell lines have devolved from human cancer cells over years or even decades under selective pressure in culture conditions. Moreover, models that have been trained on in vitro data cannot account for interactions with other types of cells. Drug-response data that are based on patient-derived cell cultures, xenografts, and organoids, on the other hand, are not available in the quantities that are needed to train high-capacity machine-learning models. We found that pre-training deep neural network models of drug sensitivity on in vitro drug-sensitivity databases before fine-tuning the model parameters on patient-derived data improves the models’ accuracy and improves the biological plausibility of the features, compared to training only on patient-derived data. From our experiments, we can conclude that pre-trained models outperform models that have been trained on the target domains in the vast majority of cases.
PLATON
(2019)
Lesson planning is both an important and demanding task—especially as part of teacher training. This paper presents the requirements for a lesson planning system and evaluates existing systems regarding these requirements. One major drawback of existing software tools is that most are limited to a text- or form-based representation of the lesson designs. In this article, a new approach with a graphical, time-based representation with (automatic) analyses methods is proposed and the system architecture and domain model are described in detail. The approach is implemented in an interactive, web-based prototype called PLATON, which additionally supports the management of lessons in units as well as the modelling of teacher and student-generated resources. The prototype was evaluated in a study with 61 prospective teachers (bachelor’s and master’s preservice teachers as well as teacher trainees in post-university teacher training) in Berlin, Germany, with a focus on usability. The results show that this approach proofed usable for lesson planning and offers positive effects for the perception of time and self-reflection.
The objective and motivation behind this research is to provide applications with easy-to-use interfaces to communities of deaf and functionally illiterate users, which enables them to work without any human assistance. Although recent years have witnessed technological advancements, the availability of technology does not ensure accessibility to information and communication technologies (ICT). Extensive use of text from menus to document contents means that deaf or functionally illiterate can not access services implemented on most computer software. Consequently, most existing computer applications pose an accessibility barrier to those who are unable to read fluently. Online technologies intended for such groups should be developed in continuous partnership with primary users and include a thorough investigation into their limitations, requirements and usability barriers. In this research, I investigated existing tools in voice, web and other multimedia technologies to identify learning gaps and explored ways to enhance the information literacy for deaf and functionally illiterate users. I worked on the development of user-centered interfaces to increase the capabilities of deaf and low literacy users by enhancing lexical resources and by evaluating several multimedia interfaces for them. The interface of the platform-independent Italian Sign Language (LIS) Dictionary has been developed to enhance the lexical resources for deaf users. The Sign Language Dictionary accepts Italian lemmas as input and provides their representation in the Italian Sign Language as output. The Sign Language dictionary has 3082 signs as set of Avatar animations in which each sign is linked to a corresponding Italian lemma. I integrated the LIS lexical resources with MultiWordNet (MWN) database to form the first LIS MultiWordNet(LMWN). LMWN contains information about lexical relations between words, semantic relations between lexical concepts (synsets), correspondences between Italian and sign language lexical concepts and semantic fields (domains). The approach enhances the deaf users’ understanding of written Italian language and shows that a relatively small set of lexicon can cover a significant portion of MWN. Integration of LIS signs with MWN made it useful tool for computational linguistics and natural language processing. The rule-based translation process from written Italian text to LIS has been transformed into service-oriented system. The translation process is composed of various modules including parser, semantic interpreter, generator, and spatial allocation planner. This translation procedure has been implemented in the Java Application Building Center (jABC), which is a framework for extreme model driven design (XMDD). The XMDD approach focuses on bringing software development closer to conceptual design, so that the functionality of a software solution could be understood by someone who is unfamiliar with programming concepts. The transformation addresses the heterogeneity challenge and enhances the re-usability of the system. For enhancing the e-participation of functionally illiterate users, two detailed studies were conducted in the Republic of Rwanda. In the first study, the traditional (textual) interface was compared with the virtual character-based interactive interface. The study helped to identify usability barriers and users evaluated these interfaces according to three fundamental areas of usability, i.e. effectiveness, efficiency and satisfaction. In another study, we developed four different interfaces to analyze the usability and effects of online assistance (consistent help) for functionally illiterate users and compared different help modes including textual, vocal and virtual character on the performance of semi-literate users. In our newly designed interfaces the instructions were automatically translated in Swahili language. All the interfaces were evaluated on the basis of task accomplishment, time consumption, System Usability Scale (SUS) rating and number of times the help was acquired. The results show that the performance of semi-literate users improved significantly when using the online assistance. The dissertation thus introduces a new development approach in which virtual characters are used as additional support for barely literate or naturally challenged users. Such components enhanced the application utility by offering a variety of services like translating contents in local language, providing additional vocal information, and performing automatic translation from text to sign language. Obviously, there is no such thing as one design solution that fits for all in the underlying domain. Context sensitivity, literacy and mental abilities are key factors on which I concentrated and the results emphasize that computer interfaces must be based on a thoughtful definition of target groups, purposes and objectives.
Computer Security deals with the detection and mitigation of threats to computer networks, data, and computing hardware. This
thesis addresses the following two computer security problems: email spam campaign and malware detection.
Email spam campaigns can easily be generated using popular dissemination tools by specifying simple grammars that serve as message templates. A grammar is disseminated to nodes of a bot net, the nodes create messages by instantiating the grammar at random. Email spam campaigns can encompass huge data volumes and therefore pose a threat to the stability of the infrastructure of email service providers that have to store them. Malware -software that serves a malicious purpose- is affecting web servers, client computers via active content, and client computers through executable files. Without the help of malware detection systems it would be easy for malware creators to collect sensitive information or to infiltrate computers.
The detection of threats -such as email-spam messages, phishing messages, or malware- is an adversarial and therefore intrinsically
difficult problem. Threats vary greatly and evolve over time. The detection of threats based on manually-designed rules is therefore
difficult and requires a constant engineering effort. Machine-learning is a research area that revolves around the analysis of data and the discovery of patterns that describe aspects of the data. Discriminative learning methods extract prediction models from data that are optimized to predict a target attribute as accurately as possible. Machine-learning methods hold the promise of automatically identifying patterns that robustly and accurately detect threats. This thesis focuses on the design and analysis of discriminative learning methods for the two computer-security problems under investigation: email-campaign and malware detection.
The first part of this thesis addresses email-campaign detection. We focus on regular expressions as a syntactic framework, because regular expressions are intuitively comprehensible by security engineers and administrators, and they can be applied as a detection mechanism in an extremely efficient manner. In this setting, a prediction model is provided with exemplary messages from an email-spam campaign. The prediction model has to generate a regular expression that reveals the syntactic pattern that underlies the entire campaign, and that a security engineers finds comprehensible and feels confident enough to use the expression to blacklist further messages at the email server. We model this problem as two-stage learning problem with structured input and output spaces which can be solved using standard cutting plane methods. Therefore we develop an appropriate loss function, and derive a decoder for the resulting optimization problem.
The second part of this thesis deals with the problem of predicting whether a given JavaScript or PHP file is malicious or benign. Recent malware analysis techniques use static or dynamic features, or both. In fully dynamic analysis, the software or script is executed and observed for malicious behavior in a sandbox environment. By contrast, static analysis is based on features that can be extracted directly from the program file. In order to bypass static detection mechanisms, code obfuscation techniques are used to spread a malicious program file in many different syntactic variants. Deobfuscating the code before applying a static classifier can be subjected to mostly static code analysis and can overcome the problem of obfuscated malicious code, but on the other hand increases the computational costs of malware detection by an order of magnitude. In this thesis we present a cascaded architecture in which a classifier first performs a static analysis of the original code and -based on the outcome of this first classification step- the code may be deobfuscated and classified again. We explore several types of features including token $n$-grams, orthogonal sparse bigrams, subroutine-hashings, and syntax-tree features and study the robustness of detection methods and feature types against the evolution of malware over time. The developed tool scans very large file collections quickly and accurately.
Each model is evaluated on real-world data and compared to reference methods. Our approach of inferring regular expressions to filter emails belonging to an email spam campaigns leads to models with a high true-positive rate at a very low false-positive rate that is an order of magnitude lower than that of a commercial content-based filter. Our presented system -REx-SVMshort- is being used by a commercial email service provider and complements content-based and IP-address based filtering.
Our cascaded malware detection system is evaluated on a high-quality data set of almost 400,000 conspicuous PHP files and a collection of more than 1,00,000 JavaScript files. From our case study we can conclude that our system can quickly and accurately process large data collections at a low false-positive rate.
Output statt Input
(2010)
Die in der Fachdidaktik Informatik im Zusammenhang mit den Bildungsstandards seit Jahren diskutierte Outputorientierung wird mittelfristig auch für die Hochschullehre verbindlich. Diese Änderung kann als Chance aufgefasst werden, aktuellen Problemen der Informatiklehre gezielt entgegenzuwirken. Basierend auf der Theorie des Constructive Alignment wird vorgeschlagen, im Zusammenhang mit der Outputorientierung eine Abstimmung von intendierter Kompetenz, Lernaktivität und Prüfung vorzunehmen. Zusätzlich profitieren Lehramtsstudenten von den im eigenen Lernprozess erworbenen Erfahrungen im Umgang mit Kompetenzen: wie diese formuliert, erarbeitet und geprüft werden. Anforderungen an die Formulierung von Kompetenzen werden untersucht, mit Beispielen belegt und Möglichkeiten zur Klassifizierung angeregt. Ein Austausch in den Fachbereichen und Fachdidaktiken über die individuell festgelegten Kompetenzen wird vorgeschlagen, um die hochschuldidaktische Diskussion zu bereichern.
The objective of this thesis is to provide new space compaction techniques for testing or concurrent checking of digital circuits. In particular, the work focuses on the design of space compactors that achieve high compaction ratio and minimal loss of testability of the circuits. In the first part, the compactors are designed for combinational circuits based on the knowledge of the circuit structure. Several algorithms for analyzing circuit structures are introduced and discussed for the first time. The complexity of each design procedure is linear with respect to the number of gates of the circuit. Thus, the procedures are applicable to large circuits. In the second part, the first structural approach for output compaction for sequential circuits is introduced. Essentially, it enhances the first part. For the approach introduced in the third part it is assumed that the structure of the circuit and the underlying fault model are unknown. The space compaction approach requires only the knowledge of the fault-free test responses for a precomputed test set. The proposed compactor design guarantees zero-aliasing with respect to the precomputed test set.
Die Orientierung am Outcome eines Lernprozesses stellt einen wichtigen Pfeiler einer kompetenzorientierten Informatiklehre dar. Im Beitrag werden Konzeption und Erfahrungen eines Projekts zur outcome-orientierten Neuausrichtung der Informatiklehre unter Berücksichtigung der Theorie des Constructive Alignment beschrieben. Nach der theoretischen Fundierung der Kompetenzproblematik wird anhand eines Formulierungsmodells ein Prozess zur Erarbeitung beobachtbarer Lernergebnisse dargestellt. Die Diskussion der Projektziele und Erfahrungen in der Umsetzung und Evaluierung unterstreichen die Chancen und Herausforderungen für eine Steigerung der Studienqualität.
Die Dissertation stellt eine neue Herangehensweise an die Lösung der Aufgabe der funktionalen Diagnostik digitaler Systeme vor. In dieser Arbeit wird eine neue Methode für die Fehlererkennung vorgeschlagen, basierend auf der Logischen Ergänzung und der Verwendung von Berger-Codes und dem 1-aus-3 Code. Die neue Fehlererkennungsmethode der Logischen Ergänzung gestattet einen hohen Optimierungsgrad der benötigten Realisationsfläche der konstruierten Fehlererkennungsschaltungen. Außerdem ist eins der wichtigen in dieser Dissertation gelösten Probleme die Synthese vollständig selbstprüfender Schaltungen.
Contemporary multi-core processors are parallel systems that also provide shared memory for programs running on them. Both the increasing number of cores in so-called many-core systems and the still growing computational power of the cores demand for memory systems that are able to deliver high bandwidths. Caches are essential components to satisfy this requirement. Nevertheless, hardware-based cache coherence in many-core chips faces practical limits to provide both coherence and high memory bandwidths. In addition, a shift away from global coherence can be observed. As a result, alternative architectures and suitable programming models need to be investigated.
This thesis focuses on fast communication for non-cache-coherent many-core architectures. Experiments are conducted on the Single-Chip Cloud Computer (SCC), a non-cache-coherent many-core processor with 48 mesh-connected cores. Although originally designed for message passing, the results of this thesis show that shared memory can be efficiently used for one-sided communication on this kind of architecture. One-sided communication enables data exchanges between processes where the receiver is not required to know the details of the performed communication. In the notion of the Message Passing Interface (MPI) standard, this type of communication allows to access memory of remote processes. In order to support this communication scheme on non-cache-coherent architectures, both an efficient process synchronization and a communication scheme with software-managed cache coherence are designed and investigated.
The process synchronization realizes the concept of the general active target synchronization scheme from the MPI standard. An existing classification of implementation approaches is extended and used to identify an appropriate class for the non-cache-coherent shared memory platform. Based on this classification, existing implementations are surveyed in order to find beneficial concepts, which are then used to design a lightweight synchronization protocol for the SCC that uses shared memory and uncached memory accesses. The proposed scheme is not prone to process skew and also enables direct communication as soon as both communication partners are ready. Experimental results show very good scaling properties and up to five times lower synchronization latency compared to a tuned message-based MPI implementation for the SCC.
For the communication, SCOSCo, a shared memory approach with software-managed cache coherence, is presented. According requirements for the coherence that fulfill MPI's separate memory model are formulated, and a lightweight implementation exploiting SCC hard- and software features is developed. Despite a discovered malfunction in the SCC's memory subsystem, the experimental evaluation of the design reveals up to five times better bandwidths and nearly four times lower latencies in micro-benchmarks compared to the SCC-tuned but message-based MPI library. For application benchmarks, like a parallel 3D fast Fourier transform, the runtime share of communication can be reduced by a factor of up to five. In addition, this thesis postulates beneficial hardware concepts that would support software-managed coherence for one-sided communication on future non-cache-coherent architectures where coherence might be only available in local subdomains but not on a global processor level.
In recent years, there has been a dramatic increase in available compute capacities. However, these “Grid resources” are rarely accessible in a continuous stream, but rather appear scattered across various machine types, platforms and operating systems, which are coupled by networks of fluctuating bandwidth. It becomes increasingly difficult for scientists to exploit available resources for their applications. We believe that intelligent, self-governing applications should be able to select resources in a dynamic and heterogeneous environment: Migrating applications determine a resource when old capacities are used up. Spawning simulations launch algorithms on external machines to speed up the main execution. Applications are restarted as soon as a failure is detected. All these actions can be taken without human interaction. A distributed compute environment possesses an intrinsic unreliability. Any application that interacts with such an environment must be able to cope with its failing components: deteriorating networks, crashing machines, failing software. We construct a reliable service infrastructure by endowing a service environment with a peer-to-peer topology. This “Grid Peer Services” infrastructure accommodates high-level services like migration and spawning, as well as fundamental services for application launching, file transfer and resource selection. It utilizes existing Grid technology wherever possible to accomplish its tasks. An Application Information Server acts as a generic information registry to all participants in a service environment. The service environment that we developed, allows applications e.g. to send a relocation requests to a migration server. The server selects a new computer based on the transmitted resource requirements. It transfers the application's checkpoint and binary to the new host and resumes the simulation. Although the Grid's underlying resource substrate is not continuous, we achieve persistent computations on Grids by relocating the application. We show with our real-world examples that a traditional genome analysis program can be easily modified to perform self-determined migrations in this service environment.
The Internet of Things (IoT) is a system of physical objects that can be discovered, monitored, controlled, or interacted with by electronic devices that communicate over various networking interfaces and eventually can be connected to the wider Internet. [Guinard and Trifa, 2016]. IoT devices are equipped with sensors and/or actuators and may be constrained in terms of memory, computational power, network bandwidth, and energy. Interoperability can help to manage such heterogeneous devices. Interoperability is the ability of different types of systems to work together smoothly. There are four levels of interoperability: physical, network and transport, integration, and data. The data interoperability is subdivided into syntactic and semantic data. Semantic data describes the meaning of data and the common understanding of vocabulary e.g. with the help of dictionaries, taxonomies, ontologies. To achieve interoperability, semantic interoperability is necessary.
Many organizations and companies are working on standards and solutions for interoperability in the IoT. However, the commercial solutions produce a vendor lock-in. They focus on centralized approaches such as cloud-based solutions. This thesis proposes a decentralized approach namely Edge Computing. Edge Computing is based on the concepts of mesh networking and distributed processing. This approach has an advantage that information collection and processing are placed closer to the sources of this information. The goals are to reduce traffic, latency, and to be robust against a lossy or failed Internet connection.
We see management of IoT devices from the network configuration management perspective. This thesis proposes a framework for network configuration management of heterogeneous, constrained IoT devices by using semantic descriptions for interoperability. The MYNO framework is an acronym for MQTT, YANG, NETCONF and Ontology. The NETCONF protocol is the IETF standard for network configuration management. The MQTT protocol is the de-facto standard in the IoT. We picked up the idea of the NETCONF-MQTT bridge, originally proposed by Scheffler and Bonneß[2017], and extended it with semantic device descriptions. These device descriptions provide a description of the device capabilities. They are based on the oneM2M Base ontology and formalized by the Semantic Web Standards.
The novel approach is using a ontology-based device description directly on a constrained device in combination with the MQTT protocol. The bridge was extended in order to query such descriptions. Using a semantic annotation, we achieved that the device capabilities are self-descriptive, machine readable and re-usable.
The concept of a Virtual Device was introduced and implemented, based on semantic device descriptions. A Virtual Device aggregates the capabilities of all devices at the edge network and contributes therefore to the scalability. Thus, it is possible to control all devices via a single RPC call.
The model-driven NETCONF Web-Client is generated automatically from this YANG model which is generated by the bridge based on the semantic device description. The Web-Client provides a user-friendly interface, offers RPC calls and displays sensor values. We demonstrate the feasibility of this approach in different use cases: sensor and actuator scenarios, as well as event configuration and triggering.
The semantic approach results in increased memory overhead. Therefore, we evaluated CBOR and RDF HDT for optimization of ontology-based device descriptions for use on constrained devices. The evaluation shows that CBOR is not suitable for long strings and RDF HDT is a promising candidate but is still a W3C Member Submission. Finally, we used an optimized JSON-LD format for the syntax of the device descriptions.
One of the security tasks of network management is the distribution of firmware updates. The MYNO Update Protocol (MUP) was developed and evaluated on constrained devices CC2538dk and 6LoWPAN. The MYNO update process is focused on freshness and authenticity of the firmware. The evaluation shows that it is challenging but feasible to bring the firmware updates to constrained devices using MQTT. As a new requirement for the next MQTT version, we propose to add a slicing feature for the better support of constrained devices. The MQTT broker should slice data to the maximum packet size specified by the device and transfer it slice-by-slice.
For the performance and scalability evaluation of MYNO framework, we setup the High Precision Agriculture demonstrator with 10 ESP-32 NodeMCU boards at the edge of the network. The ESP-32 NodeMCU boards, connected by WLAN, were equipped with six sensors and two actuators. The performance evaluation shows that the processing of ontology-based descriptions on a Raspberry Pi 3B with the RDFLib is a challenging task regarding computational power. Nevertheless, it is feasible because it must be done only once per device during the discovery process.
The MYNO framework was tested with heterogeneous devices such as CC2538dk from Texas Instruments, Arduino Yún Rev 3, and ESP-32 NodeMCU, and IP-based networks such as 6LoWPAN and WLAN.
Summarizing, with the MYNO framework we could show that the semantic approach on constrained devices is feasible in the IoT.
Das Gebiet der Netzsicherheit ist ein schwer zu lehrendes und mühsam zu lernendes Fach in der Informatikausbildung. Dies hat verschiedene Gründe, z.B. erfordert es Fachkenntnis, die jenseits von bunten Bildern zu vermitteln ist und sich dabei mit geringer Halbwertszeit weiterentwickelt. Echte Bedrohungsszenarien müssen unter Laborbedingungen nachgestellt werden, und der Umgang mit den Sicherheitswerkzeugen ist sehr komplex. Auf der einen Seite muss das System konzeptionell verstanden werden und auf der anderen Seite sind viele Details in der Konfiguration von Firewalls, Netz-Komponenten und –Werkzeugen für klassische Prüfungssituationen in der Ausbildung anzuwenden. Mit NetS-X (Network Security Experience) stellen wir einen laufenden Prototyp einer e-learning Plattform vor, mit der ein weiter Bereich von Sicherheitsszenarien vermittelt werden kann. Dabei wird der Lernende in einem Spielsystem mit Situationen konfrontiert, die er in einer echten, auf Linux basierenden typischen IT-Infrastruktur eines Unternehmens beherrschen muss. Die sicherheitsrelevanten Aktivitäten des Lernenden, z.B. der Einsatz von Monitor-Werkzeugen oder die Konfiguration von Netz-Komponenten werden dabei nicht simuliert, sondern real durchgeführt und durch Prozesse des Spielsystems beobachtet und bewertet. Autorenwerkzeuge ermöglichen den Lehrenden und Spielern, selber neue Spielsituationen, Sicherheitsszenarien oder Wissenskomponenten in das System zu integrieren.
Forschendes Lernen und die digitale Transformation sind zwei der wichtigsten Einflüsse auf die Entwicklung der Hochschuldidaktik im deutschprachigen Raum. Während das forschende Lernen als normative Theorie das sollen beschreibt, geben die digitalen Werkzeuge, alte wie neue, das können in vielen Bereichen vor.
In der vorliegenden Arbeit wird ein Prozessmodell aufgestellt, was den Versuch unternimmt, das forschende Lernen hinsichtlich interaktiver, gruppenbasierter Prozesse zu systematisieren. Basierend auf dem entwickelten Modell wurde ein Softwareprototyp implementiert, der den gesamten Forschungsprozess begleiten kann. Dabei werden Gruppenformation, Feedback- und Reflexionsprozesse und das Peer Assessment mit Bildungstechnologien unterstützt. Die Entwicklungen wurden in einem qualitativen Experiment eingesetzt, um Systemwissen über die Möglichkeiten und Grenzen der digitalen Unterstützung von forschendem Lernen zu gewinnen.
A project involving the composition of a number of pieces
of music by public participants revealed levels of engagement with and
mastery of complex music technologies by a number of secondary student
volunteers. This paper reports briefly on some initial findings of
that project and seeks to illuminate an understanding of computational
thinking across the curriculum.
MUP
(2020)
Message Queuing Telemetry Transport (MQTT) is one of the dominating protocols for edge- and cloud-based Internet of Things (IoT) solutions. When a security vulnerability of an IoT device is known, it has to be fixed as soon as possible. This requires a firmware update procedure. In this paper, we propose a secure update protocol for MQTT-connected devices which ensures the freshness of the firmware, authenticates the new firmware and considers constrained devices. We show that the update protocol is easy to integrate in an MQTT-based IoT network using a semantic approach. The feasibility of our approach is demonstrated by a detailed performance analysis of our prototype implementation on a IoT device with 32 kB RAM. Thereby, we identify design issues in MQTT 5 which can help to improve the support of constrained devices.
The innovation of information techniques has changed many aspects of our life. In health care field, we can obtain, manage and communicate high-quality large volumetric image data by computer integrated devices, to support medical care. In this dissertation I propose several promising methods that could assist physicians in processing, observing and communicating the image data. They are included in my three research aspects: telemedicine integration, medical image visualization and image segmentation. And these methods are also demonstrated by the demo software that I developed. One of my research point focuses on medical information storage standard in telemedicine, for example DICOM, which is the predominant standard for the storage and communication of medical images. I propose a novel 3D image data storage method, which was lacking in current DICOM standard. I also created a mechanism to make use of the non-standard or private DICOM files. In this thesis I present several rendering techniques on medical image visualization to offer different display manners, both 2D and 3D, for example, cut through data volume in arbitrary degree, rendering the surface shell of the data, and rendering the semi-transparent volume of the data. A hybrid segmentation approach, designed for semi-automated segmentation of radiological image, such as CT, MRI, etc, is proposed in this thesis to get the organ or interested area from the image. This approach takes advantage of the region-based method and boundary-based methods. Three steps compose the hybrid approach: the first step gets coarse segmentation by fuzzy affinity and generates homogeneity operator; the second step divides the image by Voronoi Diagram and reclassifies the regions by the operator to refine segmentation from the previous step; the third step handles vague boundary by level set model. Topics for future research are mentioned in the end, including new supplement for DICOM standard for segmentation information storage, visualization of multimodal image information, and improvement of the segmentation approach to higher dimension.
Virtual 3D city and landscape models are the main subject investigated in this thesis. They digitally represent urban space and have many applications in different domains, e.g., simulation, cadastral management, and city planning. Visualization is an elementary component of these applications. Photo-realistic visualization with an increasingly high degree of detail leads to fundamental problems for comprehensible visualization. A large number of highly detailed and textured objects within a virtual 3D city model may create visual noise and overload the users with information. Objects are subject to perspective foreshortening and may be occluded or not displayed in a meaningful way, as they are too small. In this thesis we present abstraction techniques that automatically process virtual 3D city and landscape models to derive abstracted representations. These have a reduced degree of detail, while essential characteristics are preserved. After introducing definitions for model, scale, and multi-scale representations, we discuss the fundamentals of map generalization as well as techniques for 3D generalization. The first presented technique is a cell-based generalization of virtual 3D city models. It creates abstract representations that have a highly reduced level of detail while maintaining essential structures, e.g., the infrastructure network, landmark buildings, and free spaces. The technique automatically partitions the input virtual 3D city model into cells based on the infrastructure network. The single building models contained in each cell are aggregated to abstracted cell blocks. Using weighted infrastructure elements, cell blocks can be computed on different hierarchical levels, storing the hierarchy relation between the cell blocks. Furthermore, we identify initial landmark buildings within a cell by comparing the properties of individual buildings with the aggregated properties of the cell. For each block, the identified landmark building models are subtracted using Boolean operations and integrated in a photo-realistic way. Finally, for the interactive 3D visualization we discuss the creation of the virtual 3D geometry and their appearance styling through colors, labeling, and transparency. We demonstrate the technique with example data sets. Additionally, we discuss applications of generalization lenses and transitions between abstract representations. The second technique is a real-time-rendering technique for geometric enhancement of landmark objects within a virtual 3D city model. Depending on the virtual camera distance, landmark objects are scaled to ensure their visibility within a specific distance interval while deforming their environment. First, in a preprocessing step a landmark hierarchy is computed, this is then used to derive distance intervals for the interactive rendering. At runtime, using the virtual camera distance, a scaling factor is computed and applied to each landmark. The scaling factor is interpolated smoothly at the interval boundaries using cubic Bézier splines. Non-landmark geometry that is near landmark objects is deformed with respect to a limited number of landmarks. We demonstrate the technique by applying it to a highly detailed virtual 3D city model and a generalized 3D city model. In addition we discuss an adaptation of the technique for non-linear projections and mobile devices. The third technique is a real-time rendering technique to create abstract 3D isocontour visualization of virtual 3D terrain models. The virtual 3D terrain model is visualized as a layered or stepped relief. The technique works without preprocessing and, as it is implemented using programmable graphics hardware, can be integrated with minimal changes into common terrain rendering techniques. Consequently, the computation is done in the rendering pipeline for each vertex, primitive, i.e., triangle, and fragment. For each vertex, the height is quantized to the nearest isovalue. For each triangle, the vertex configuration with respect to their isovalues is determined first. Using the configuration, the triangle is then subdivided. The subdivision forms a partial step geometry aligned with the triangle. For each fragment, the surface appearance is determined, e.g., depending on the surface texture, shading, and height-color-mapping. Flexible usage of the technique is demonstrated with applications from focus+context visualization, out-of-core terrain rendering, and information visualization. This thesis presents components for the creation of abstract representations of virtual 3D city and landscape models. Re-using visual language from cartography, the techniques enable users to build on their experience with maps when interpreting these representations. Simultaneously, characteristics of 3D geovirtual environments are taken into account by addressing and discussing, e.g., continuous scale, interaction, and perspective.
Die nachhaltige Integration von Blended Learning in den Informatik-Lehrbetrieb von Präsenzhochschulen und die Qualitätssicherung der Lehre mit digitalen Medien beruht nicht nur auf der Verfügbarkeit von Lernmaterialien und dem Zugang zu Lernplattformen, sondern erfordert auch Qualifizierungsmaßnahmen für die Lehrenden. Am Beispiel der Gestaltung von vorlesungsbegleitenden Übungen in der universitären Informatikausbildung wird ein Konzept für die Schulung von Tutoren vorgestellt, das sich an den Erfordernissen des Übungsbetriebs und den unterschiedlichen Arbeits- und Lernkontexten der künftigen Tutoren orientiert. Das Konzept basiert auf mehrjährigen Praxiserfahrungen mit Schulungsworkshops für Tutoren in der Informatik, die nun aufgrund aktueller didaktischer Konzepte zum Blended Learning und unter Berücksichtigung von Umfrageergebnissen unter studentischen Tutoren modifiziert wurden. Das neu entwickelte modulare Konzept zur Tutorenschulung befindet sich aktuell in einer erweiterten Pilotphase.
Answer Set Programming (ASP) is a declarative problem solving approach, combining a rich yet simple modeling language with high-performance solving capabilities. Although this has already resulted in various applications, certain aspects of such applications are more naturally modeled using variables over finite domains, for accounting for resources, fine timings, coordinates, or functions. Our goal is thus to extend ASP with constraints over integers while preserving its declarative nature. This allows for fast prototyping and elaboration tolerant problem descriptions of resource related applications. The resulting paradigm is called Constraint Answer Set Programming (CASP).
We present three different approaches for solving CASP problems. The first one, a lazy, modular approach combines an ASP solver with an external system for handling constraints. This approach has the advantage that two state of the art technologies work hand in hand to solve the problem, each concentrating on its part of the problem. The drawback is that inter-constraint dependencies cannot be communicated back to the ASP solver, impeding its learning algorithm. The second approach translates all constraints to ASP. Using the appropriate encoding techniques, this results in a very fast, monolithic system. Unfortunately, due to the large, explicit representation of constraints and variables, translation techniques are restricted to small and mid-sized domains. The third approach merges the lazy and the translational approach, combining the strength of both while removing their weaknesses. To this end, we enhance the dedicated learning techniques of an ASP solver with the inferences of the translating approach in a lazy way. That is, the important knowledge is only made explicit when needed.
By using state of the art techniques from neighboring fields, we provide ways to tackle real world, industrial size problems. By extending CASP to reactive solving, we open up new application areas such as online planning with continuous domains and durations.
As a result of the Bologna reform of educational systems in
Europe the outcome orientation of learning processes, competence-oriented
descriptions of the curricula and competence-oriented assessment
procedures became standard also in Computer Science Education
(CSE). The following keynote addresses important issues of shaping
a CSE competence model especially in the area of informatics system
comprehension and object-oriented modelling. Objectives and research
methodology of the project MoKoM (Modelling and Measurement
of Competences in CSE) are explained. Firstly, the CSE competence
model was derived based on theoretical concepts and then secondly the
model was empirically examined and refined using expert interviews.
Furthermore, the paper depicts the development and examination of
a competence measurement instrument, which was derived from the
competence model. Therefore, the instrument was applied to a large
sample of students at the gymnasium’s upper class level. Subsequently,
efforts to develop a competence level model, based on the retrieved empirical
results and on expert ratings are presented. Finally, further demands
on research on competence modelling in CSE will be outlined.
Die Projektierung und Abwicklung sowie die statische und dynamische Analyse von Geschäftsprozessen im Bereich des Verwaltens und Regierens auf kommunaler, Länder- wie auch Bundesebene mit Hilfe von Informations- und Kommunikationstechniken beschäftigen Politiker und Strategen für Informationstechnologie ebenso wie die Öffentlichkeit seit Langem.
Der hieraus entstandene Begriff E-Government wurde in der Folge aus den unterschiedlichsten technischen, politischen und semantischen Blickrichtungen beleuchtet.
Die vorliegende Arbeit konzentriert sich dabei auf zwei Schwerpunktthemen:
• Das erste Schwerpunktthema behandelt den Entwurf eines hierarchischen Architekturmodells, für welches sieben hierarchische Schichten identifiziert werden können. Diese erscheinen notwendig, aber auch hinreichend, um den allgemeinen Fall zu beschreiben.
Den Hintergrund hierfür liefert die langjährige Prozess- und Verwaltungserfahrung als Leiter der EDV-Abteilung der Stadtverwaltung Landshut, eine kreisfreie Stadt mit rund 69.000 Einwohnern im Nordosten von München. Sie steht als Repräsentant für viele Verwaltungsvorgänge in der Bundesrepublik Deutschland und ist dennoch als Analyseobjekt in der Gesamtkomplexität und Prozessquantität überschaubar.
Somit können aus der Analyse sämtlicher Kernabläufe statische und dynamische Strukturen extrahiert und abstrakt modelliert werden.
Die Schwerpunkte liegen in der Darstellung der vorhandenen Bedienabläufe in einer Kommune. Die Transformation der Bedienanforderung in einem hierarchischen System, die Darstellung der Kontroll- und der Operationszustände in allen Schichten wie auch die Strategie der Fehlererkennung und Fehlerbehebung schaffen eine transparente Basis für umfassende Restrukturierungen und Optimierungen.
Für die Modellierung wurde FMC-eCS eingesetzt, eine am Hasso-Plattner-Institut für Softwaresystemtechnik GmbH (HPI) im Fachgebiet Kommunikationssysteme entwickelte Methodik zur Modellierung zustandsdiskreter Systeme unter Berücksichtigung möglicher Inkonsistenzen (Betreuer: Prof. Dr.-Ing. Werner Zorn [ZW07a, ZW07b]).
• Das zweite Schwerpunktthema widmet sich der quantitativen Modellierung und Optimierung von E-Government-Bediensystemen, welche am Beispiel des Bürgerbüros der Stadt Landshut im Zeitraum 2008 bis 2015 durchgeführt wurden. Dies erfolgt auf Basis einer kontinuierlichen Betriebsdatenerfassung mit aufwendiger Vorverarbeitung zur Extrahierung mathematisch beschreibbarer Wahrscheinlichkeitsverteilungen.
Der hieraus entwickelte Dienstplan wurde hinsichtlich der erzielbaren Optimierungen im dauerhaften Echteinsatz verifiziert.
[ZW07a] Zorn, Werner: «FMC-QE A New Approach in Quantitative Modeling», Vortrag anlässlich: MSV'07- The 2007 International Conference on Modeling, Simulation and Visualization Methods WorldComp2007, Las Vegas, 28.6.2007.
[ZW07b] Zorn, Werner: «FMC-QE, A New Approach in Quantitative Modeling», Veröffentlichung, Hasso-Plattner-Institut für Softwaresystemtechnik an der Universität Potsdam, 28.6.2007.
Digitalisierung ermöglicht es uns, mit Partnern (z.B. Unternehmen, Institutionen) in einer IT-unterstützten Umgebung zu interagieren und Tätigkeiten auszuführen, die vormals manuell erledigt wurden. Ein Ziel der Digitalisierung ist dabei, Dienstleistungen unterschiedlicher fachlicher Domänen zu Prozessen zu kombinieren und vielen Nutzergruppen bedarfsgerecht zugänglich zu machen. Hierzu stellen Anbieter technische Dienste bereit, die in unterschiedliche Anwendungen integriert werden können.
Die Digitalisierung stellt die Anwendungsentwicklung vor neue Herausforderungen. Ein Aspekt ist die bedarfsgerechte Anbindung von Nutzern an Dienste. Zur Interaktion menschlicher Nutzer mit den Diensten werden Benutzungsschnittstellen benötigt, die auf deren Bedürfnisse zugeschnitten sind. Hierzu werden Varianten für spezifische Nutzergruppen (fachliche Varianten) und variierende Umgebungen (technische Varianten) benötigt. Zunehmend müssen diese mit Diensten anderer Anbieter kombiniert werden können, um domänenübergreifend Prozesse zu Anwendungen mit einem erhöhten Mehrwert für den Endnutzer zu verknüpfen (z.B. eine Flugbuchung mit einer optionalen Reiseversicherung).
Die Vielfältigkeit der Varianten lässt die Erstellung von Benutzungsschnittstellen komplex und die Ergebnisse sehr individuell erscheinen. Daher werden die Varianten in der Praxis vorwiegend manuell erstellt. Dies führt zur parallelen Entwicklung einer Vielzahl sehr ähnlicher Anwendungen, die nur geringes Potential zur Wiederverwendung besitzen. Die Folge sind hohe Aufwände bei Erstellung und Wartung. Dadurch wird häufig auf die Unterstützung kleiner Nutzerkreise mit speziellen Anforderungen verzichtet (z.B. Menschen mit physischen Einschränkungen), sodass diese weiterhin von der Digitalisierung ausgeschlossen bleiben.
Die Arbeit stellt eine konsistente Lösung für diese neuen Herausforderungen mit den Mitteln der modellgetriebenen Entwicklung vor. Sie präsentiert einen Ansatz zur Modellierung von Benutzungsschnittstellen, Varianten und Kompositionen und deren automatischer Generierung für digitale Dienste in einem verteilten Umfeld. Die Arbeit schafft eine Lösung zur Wiederverwendung und gemeinschaftlichen Nutzung von Benutzungsschnittstellen über Anbietergrenzen hinweg. Sie führt zu einer Infrastruktur, in der eine Vielzahl von Anbietern ihre Expertise in gemeinschaftliche Anwendungen einbringen können.
Die Beiträge bestehen im Einzelnen in Konzepten und Metamodellen zur Modellierung von Benutzungsschnittstellen, Varianten und Kompositionen sowie einem Verfahren zu deren vollständig automatisierten Transformation in funktionale Benutzungsschnittstellen. Zur Umsetzung der gemeinschaftlichen Nutzbarkeit werden diese ergänzt um eine universelle Repräsentation der Modelle, einer Methodik zur Anbindung unterschiedlicher Dienst-Anbieter sowie einer Architektur zur verteilten Nutzung der Artefakte und Verfahren in einer dienstorientierten Umgebung.
Der Ansatz bietet die Chance, unterschiedlichste Menschen bedarfsgerecht an der Digitalisierung teilhaben zu lassen. Damit setzt die Arbeit Impulse für zukünftige Methoden zur Anwendungserstellung in einem zunehmend vielfältigen Umfeld.
Mit zunehmender Komplexität technischer Softwaresysteme ist die Nachfrage an produktiveren Methoden und Werkzeugen auch im sicherheitskritischen Umfeld gewachsen. Da insbesondere objektorientierte und modellbasierte Ansätze und Methoden ausgezeichnete Eigenschaften zur Entwicklung großer und komplexer Systeme besitzen, ist zu erwarten, dass diese in naher Zukunft selbst bis in sicherheitskritische Bereiche der Softwareentwicklung vordringen. Mit der Unified Modeling Language Real-Time (UML-RT) wird eine Softwareentwicklungsmethode für technische Systeme durch die Object Management Group (OMG) propagiert. Für den praktischen Einsatz im technischen und sicherheitskritischen Umfeld muss diese Methode nicht nur bestimmte technische Eigenschaften, beispielsweise temporale Analysierbarkeit, besitzen, sondern auch in einen bestehenden Qualitätssicherungsprozess integrierbar sein. Ein wichtiger Aspekt der Integration der UML-RT in ein qualitätsorientiertes Prozessmodell, beispielsweise in das V-Modell, ist die Verfügbarkeit von ausgereiften Konzepten und Methoden für einen systematischen Modultest. Der Modultest dient als erste Qualititätssicherungsphase nach der Implementierung der Fehlerfindung und dem Qualitätsnachweis für jede separat prüfbare Softwarekomponente eines Systems. Während dieser Phase stellt die Durchführung von systematischen Tests die wichtigste Qualitätssicherungsmaßnahme dar. Während zum jetzigen Zeitpunkt zwar ausgereifte Methoden und Werkzeuge für die modellbasierte Softwareentwicklung zur Verfügung stehen, existieren nur wenig überzeugende Lösungen für eine systematische modellbasierte Modulprüfung. Die durchgängige Verwendung ausführbarer Modelle und Codegenerierung stellen wesentliche Konzepte der modellbasierten Softwareentwicklung dar. Sie dienen der konstruktiven Fehlerreduktion durch Automatisierung ansonsten fehlerträchtiger, manueller Vorgänge. Im Rahmen einer modellbasierten Qualitätssicherung sollten diese Konzepte konsequenterweise in die späteren Qualitätssicherungsphasen transportiert werden. Daher ist eine wesentliche Forderung an ein Verfahren zur modellbasierten Modulprüfung ein möglichst hoher Grad an Automatisierung. In aktuellen Entwicklungen hat sich für die Generierung von Testfällen auf Basis von Zustandsautomaten die Verwendung von Model Checking als effiziente und an die vielfältigsten Testprobleme anpassbare Methode bewährt. Der Ansatz des Model Checking stammt ursprünglich aus dem Entwurf von Kommunikationsprotokollen und wurde bereits erfolgreich auf verschiedene Probleme der Modellierung technischer Software angewendet. Insbesondere in der Gegenwart ausführbarer, automatenbasierter Modelle erscheint die Verwendung von Model Checking sinnvoll, das die Existenz einer formalen, zustandsbasierten Spezifikation voraussetzt. Ein ausführbares, zustandsbasiertes Modell erfüllt diese Anforderungen in der Regel. Aus diesen Gründen ist die Wahl eines Model Checking Ansatzes für die Generierung von Testfällen im Rahmen eines modellbasierten Modultestverfahrens eine logische Konsequenz. Obwohl in der aktuellen Spezifikation der UML-RT keine eindeutigen Aussagen über den zur Verhaltensbeschreibung zu verwendenden Formalismus gemacht werden, ist es wahrscheinlich, dass es sich bei der UML-RT um eine zu Real-Time Object-Oriented Modeling (ROOM) kompatible Methode handelt. Alle in dieser Arbeit präsentierten Methoden und Ergebnisse sind somit auf die kommende UML-RT übertragbar und von sehr aktueller Bedeutung. Aus den genannten Gründen verfolgt diese Arbeit das Ziel, die analytische Qualitätssicherung in der modellbasierten Softwareentwicklung mittels einer modellbasierten Methode für den Modultest zu verbessern. Zu diesem Zweck wird eine neuartige Testmethode präsentiert, die auf automatenbasierten Verhaltensmodellen und CTL Model Checking basiert. Die Testfallgenerierung kann weitgehend automatisch erfolgen, um Fehler durch menschlichen Einfluss auszuschließen. Das entwickelte Modultestverfahren ist in die technischen Konzepte Model Driven Architecture und ROOM, beziehungsweise UML-RT, sowie in die organisatorischen Konzepte eines qualitätsorientierten Prozessmodells, beispielsweise das V-Modell, integrierbar.
Gerade in den letzten Jahren erfuhr Open Source Software (OSS) eine zunehmende Verbreitung und Popularität und hat sich in verschiedenen Anwendungsdomänen etabliert. Die Prozesse, welche sich im Kontext der OSS-Entwicklung (auch: OSSD – Open Source Software-Development) evolutionär herausgebildet haben, weisen in den verschiedenen OSS-Entwicklungsprojekten z.T. ähnliche Eigenschaften und Strukturen auf und auch die involvierten Entitäten, wie z.B. Artefakte, Rollen oder Software-Werkzeuge sind weitgehend miteinander vergleichbar. Dies motiviert den Gedanken, ein verallgemeinerbares Modell zu entwickeln, welches die generalisierbaren Entwicklungsprozesse im Kontext von OSS zu einem übertragbaren Modell abstrahiert. Auch in der Wissenschaftsdisziplin des Software Engineering (SE) wurde bereits erkannt, dass sich der OSSD-Ansatz in verschiedenen Aspekten erheblich von klassischen (proprietären) Modellen des SE unterscheidet und daher diese Methoden einer eigenen wissenschaftlichen Betrachtung bedürfen. In verschiedenen Publikationen wurden zwar bereits einzelne Aspekte der OSS-Entwicklung analysiert und Theorien über die zugrundeliegenden Entwicklungsmethoden formuliert, aber es existiert noch keine umfassende Beschreibung der typischen Prozesse der OSSD-Methodik, die auf einer empirischen Untersuchung existierender OSS-Entwicklungsprojekte basiert. Da dies eine Voraussetzung für die weitere wissenschaftliche Auseinandersetzung mit OSSD-Prozessen darstellt, wird im Rahmen dieser Arbeit auf der Basis vergleichender Fallstudien ein deskriptives Modell der OSSD-Prozesse hergeleitet und mit Modellierungselementen der UML formalisiert beschrieben. Das Modell generalisiert die identifizierten Prozesse, Prozessentitäten und Software-Infrastrukturen der untersuchten OSSD-Projekte. Es basiert auf einem eigens entwickelten Metamodell, welches die zu analysierenden Entitäten identifiziert und die Modellierungssichten und -elemente beschreibt, die zur UML-basierten Beschreibung der Entwicklungsprozesse verwendet werden. In einem weiteren Arbeitsschritt wird eine weiterführende Analyse des identifizierten Modells durchgeführt, um Implikationen, und Optimierungspotentiale aufzuzeigen. Diese umfassen beispielsweise die ungenügende Plan- und Terminierbarkeit von Prozessen oder die beobachtete Tendenz von OSSD-Akteuren, verschiedene Aktivitäten mit unterschiedlicher Intensität entsprechend der subjektiv wahrgenommenen Anreize auszuüben, was zur Vernachlässigung einiger Prozesse führt. Anschließend werden Optimierungszielstellungen dargestellt, die diese Unzulänglichkeiten adressieren, und ein Optimierungsansatz zur Verbesserung des OSSD-Modells wird beschrieben. Dieser Ansatz umfasst die Erweiterung der identifizierten Rollen, die Einführung neuer oder die Erweiterung bereits identifizierter Prozesse und die Modifikation oder Erweiterung der Artefakte des generalisierten OSS-Entwicklungsmodells. Die vorgestellten Modellerweiterungen dienen vor allem einer gesteigerten Qualitätssicherung und der Kompensation von vernachlässigten Prozessen, um sowohl die entwickelte Software- als auch die Prozessqualität im OSSD-Kontext zu verbessern. Desweiteren werden Softwarefunktionalitäten beschrieben, welche die identifizierte bestehende Software-Infrastruktur erweitern und eine gesamtheitlichere, softwaretechnische Unterstützung der OSSD-Prozesse ermöglichen sollen. Abschließend werden verschiedene Anwendungsszenarien der Methoden des OSS-Entwicklungsmodells, u.a. auch im kommerziellen SE, identifiziert und ein Implementierungsansatz basierend auf der OSS GENESIS vorgestellt, der zur Implementierung und Unterstützung des OSSD-Modells verwendet werden kann.
Biology has made great progress in identifying and measuring the building blocks of life. The availability of high-throughput methods in molecular biology has dramatically accelerated the growth of biological knowledge for various organisms. The advancements in genomic, proteomic and metabolomic technologies allow for constructing complex models of biological systems. An increasing number of biological repositories is available on the web, incorporating thousands of biochemical reactions and genetic regulations. Systems Biology is a recent research trend in life science, which fosters a systemic view on biology. In Systems Biology one is interested in integrating the knowledge from all these different sources into models that capture the interaction of these entities. By studying these models one wants to understand the emerging properties of the whole system, such as robustness. However, both measurements as well as biological networks are prone to considerable incompleteness, heterogeneity and mutual inconsistency, which makes it highly non-trivial to draw biologically meaningful conclusions in an automated way. Therefore, we want to promote Answer Set Programming (ASP) as a tool for discrete modeling in Systems Biology. ASP is a declarative problem solving paradigm, in which a problem is encoded as a logic program such that its answer sets represent solutions to the problem. ASP has intrinsic features to cope with incompleteness, offers a rich modeling language and highly efficient solving technology. We present ASP solutions, for the analysis of genetic regulatory networks, determining consistency with observed measurements and identifying minimal causes for inconsistency. We extend this approach for computing minimal repairs on model and data that restore consistency. This method allows for predicting unobserved data even in case of inconsistency. Further, we present an ASP approach to metabolic network expansion. This approach exploits the easy characterization of reachability in ASP and its various reasoning methods, to explore the biosynthetic capabilities of metabolic reaction networks and generate hypotheses for extending the network. Finally, we present the BioASP library, a Python library which encapsulates our ASP solutions into the imperative programming paradigm. The library allows for an easy integration of ASP solution into system rich environments, as they exist in Systems Biology.
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.
Im Rahmen eines interdisziplinären studentischen Projekts wurde ein Framework für mobile pervasive Lernspiele entwickelt. Am Beispiel des historischen Lernortes Park Sanssouci wurde auf dieser Grundlage ein Lernspiel für Schülerinnen und Schüler implementiert. Die geplante Evaluation soll die Lernwirksamkeit von geobasierten mobilen Lernspielen messen. Dazu wird die Intensität des Flow-Erlebens mit einer ortsgebundenen alternativen Umsetzung verglichen.
Mit hochschuldidaktischer Forschung zur Informatik soll aus einem traditionellen Hardwarepraktikum ein attraktives Entwurfs- und Anwendungspraktikum für Mikrosysteme (MSE) werden, das ein unverzichtbarer Bestandteil des Informatikstudiums ist. Diese Neugestaltung der Lehre wurde aufgrund des Bologna-Prozesses und der zunehmenden Präsenz multifunktionaler eingebetteter Mikrosysteme (EMS) im täglichen Leben notwendig. Ausgehend von einer Lehrveranstaltungsanalyse werden Vorschläge für die Kompetenzorientierung abgeleitet. Es wird gezeigt, dass für eine Verfeinerung des Ansatzes ein wissenschaftlich fundiertes Verständnis der erwarteten Kompetenzen erforderlich ist. Für den aufgezeigten Forschungsbedarf werden ein Ansatz zur Beschreibung des notwendigen Mikrosystemverständnisses dargestellt und Forschungsfelder zu Aspekten des Kompetenzbegriffs im Kontext der Lehrveranstaltung beschrieben.
Reliable and robust data processing is one of the hardest requirements for systems in fields such as medicine, security, automotive, aviation, and space, to prevent critical system failures caused by changes in operating or environmental conditions. In particular, Signal Integrity (SI) effects such as crosstalk may distort the signal information in sensitive mixed-signal designs. A challenge for hardware systems used in the space are radiation effects. Namely, Single Event Effects (SEEs) induced by high-energy particle hits may lead to faulty computation, corrupted configuration settings, undesired system behavior, or even total malfunction.
Since these applications require an extra effort in design and implementation, it is beneficial to master the standard cell design process and corresponding design flow methodologies optimized for such challenges. Especially for reliable, low-noise differential signaling logic such as Current Mode Logic (CML), a digital design flow is an orthogonal approach compared to traditional manual design. As a consequence, mandatory preliminary considerations need to be addressed in more detail. First of all, standard cell library concepts with suitable cell extensions for reliable systems and robust space applications have to be elaborated. Resulting design concepts at the cell level should enable the logical synthesis for differential logic design or improve the radiation-hardness. In parallel, the main objectives of the proposed cell architectures are to reduce the occupied area, power, and delay overhead. Second, a special setup for standard cell characterization is additionally required for a proper and accurate logic gate modeling. Last but not least, design methodologies for mandatory design flow stages such as logic synthesis and place and route need to be developed for the respective hardware systems to keep the reliability or the radiation-hardness at an acceptable level.
This Thesis proposes and investigates standard cell-based design methodologies and techniques for reliable and robust hardware systems implemented in a conventional semi-conductor technology. The focus of this work is on reliable differential logic design and robust radiation-hardening-by-design circuits. The synergistic connections of the digital design flow stages are systematically addressed for these two types of hardware systems. In more detail, a library for differential logic is extended with single-ended pseudo-gates for intermediate design steps to support the logic synthesis and layout generation with commercial Computer-Aided Design (CAD) tools. Special cell layouts are proposed to relax signal routing. A library set for space applications is similarly extended by novel Radiation-Hardening-by-Design (RHBD) Triple Modular Redundancy (TMR) cells, enabling a one fault correction. Therein, additional optimized architectures for glitch filter cells, robust scannable and self-correcting flip-flops, and clock-gates are proposed. The circuit concepts and the physical layout representation views of the differential logic gates and the RHBD cells are discussed. However, the quality of results of designs depends implicitly on the accuracy of the standard cell characterization which is examined for both types therefore. The entire design flow is elaborated from the hardware design description to the layout representations. A 2-Phase routing approach together with an intermediate design conversion step is proposed after the initial place and route stage for reliable, pure differential designs, whereas a special constraining for RHBD applications in a standard technology is presented.
The digital design flow for differential logic design is successfully demonstrated on a reliable differential bipolar CML application. A balanced routing result of its differential signal pairs is obtained by the proposed 2-Phase-routing approach. Moreover, the elaborated standard cell concepts and design methodology for RHBD circuits are applied to the digital part of a 7.5-15.5 MSPS 14-bit Analog-to-Digital Converter (ADC) and a complex microcontroller architecture. The ADC is implemented in an unhardened standard semiconductor technology and successfully verified by electrical measurements. The overhead of the proposed hardening approach is additionally evaluated by design exploration of the microcontroller application. Furthermore, the first obtained related measurement results of novel RHBD-∆TMR flip-flops show a radiation-tolerance up to a threshold Linear Energy Transfer (LET) of 46.1, 52.0, and 62.5 MeV cm2 mg-1 and savings in silicon area of 25-50 % for selected TMR standard cell candidates.
As a conclusion, the presented design concepts at the cell and library levels, as well as the design flow modifications are adaptable and transferable to other technology nodes. In particular, the design of hybrid solutions with integrated reliable differential logic modules together with robust radiation-tolerant circuit parts is enabled by the standard cell concepts and design methods proposed in this work.