Conjunctive queries (CQs), the standard query language in databases, have recently gained significant attention for querying DL knowledge bases. Several different techniques are available for a wide range of DLs. Nevertheless, for OWL DL and OWL 2, decidability of CQ entailment is an open problem. So far, the combination of nominals, inverse roles, and number restrictions caused unsolvable problems. We tackle this problem and present a decidability result for entailment of unions of CQs in a DL with all three problematic constructors. For queries with only simple roles, our result also shows decidability in the logic that underpins OWL DL.
Bio:
Sebastian Rudolph is senior researcher and project leader at the Institute AIFB, Karlsruhe Institute of Technology (KIT). He obtained his PhD in mathematics at the Institute for Algebra at the Dresden University of Technology in 2006. His active research interests include algebra, complexity theory, logic, machine learning, optimization, database theory, and computational linguistics. Sebastian coauthored two textbooks on the foundations of the Semantic Web. He is a guest lecturer at Heidelberg University, guest researcher at FZI Karlsruhe, and he was a member of the W3C OWL Working Group. As a guest researcher, he visited Oxford University, the Technical University of Vienna and the Laboratoire d′Informatique, de Robotique et de Microélectronique de Montpellier.
In classic information flow control (IFC), noninterference guarantees that no information flows from secret input channels to public output channels. However, this notion turned out to be overly restrictive as many intuitively secure programs do allow some release, and thus intransitive noninterference allows declassification. We developed a static analysis that allows intransitive noninterference based on Program Dependence Graphs. In contrast to type systems that annotate variables, our approach annotates information sources and sinks. Our approach is flow- and context-sensitive and because it is based on an industrial strength Program Dependence Generator (CodeSurfer from GrammaTech), it allows IFC for realistic C programs.
Bio:
Jens Krinke is lecturer in the Department of Computer Science, King's College London, and Deputy Director of CREST - the Centre for Research on Evolution, Search and Testing. His current research topics include program analysis for software engineering purposes, in particular for bug detection, taint analysis and information flow control. Currently, he also works on Clone Detection and Code Provenance.
Time: Thursday 4pm, Location: SBS95, E4.040
As Fred Brooks famously noted, change is an essential characteristic of software development, as software systems must respond to evolving requirements, platforms, and other environmental pressures. In this talk, we discuss the concept of software evolution from several perspectives. We examine how it relates to and differs from software maintenance. We discuss insights about software evolution arising from Lehman’s laws of software evolution and the staged lifecycle model of Bennett and Rajlich. We compare software evolution to other kinds of evolution, from science and social sciences, and we examine the forces that shape change. Finally, we discuss the changing nature of software in general as it relates to evolution, and we propose open challenges and future directions for software evolution research.
This is joint work with Prof Daniel German of the University of Victoria, and is based on an invited paper for the Frontiers of Software Maintenance track at the 2008 IEEE International Conference on Software Maintenance.
Bio:
Michael W. Godfrey is an Associate Professor in the David R.
Cheriton School of Computer Science at the University of Waterloo
(Canada), where he is also a member of SWAG, the Software Architecture
Group. Between 2001 and 2006, he held an Associate Industrial Research
Chair in telecommunications software engineering sponsored by Nortel
Networks and NSERC. He holds a PhD in Computer Science from the
University of Toronto (1997) and was previously a faculty member at
Cornell University. His main research area is software evolution:
understanding how and why software changes over time. His research
interests include evidence-based software engineering, software clone
analysis, software tool design, reverse engineering, and program
comprehension.
Die Integration von Wissen aus heterogenen Wissensquellen erfordert u.a. die Behandlung von terminologischen Konflikten, die durch die Ambiguität von Symbolen erklärt werden können. Im Vortrag wird ein Ansatz zur semantischen Integration bzgl. eines Integrationsszenarios vorgestellt, in dem die zu integrierenden Wissensquellen gut entwickelte und verwandte Ontologien mit potentiellen Ambiguitätskonflikten sind. Neben der Darstellung von postulatsorientierten Adäquatheitskriterien für dieses Integrationsszenario werden im Vortrag konkrete Integrationsoperatoren beschrieben, die auf dem Prinzip der Reinterpretation beruhen und die auf Techniken der Belief-Revision zurückgreifen. Die Gemeinsamkeiten und Unterschiede zwischen klassischen Belief-Revisionsfunktionen und Reinterpretationsoperatoren werden anhand von erfüllten Postulaten und anhand der Konstruktionsprinzipien erläutert.
Qualitative Spatial and Temporal Reasoning (QSTR) is the subfield of knowledge representation and symbolic reasoning that is involved with infinite spatial and temporal domains. Qualitative representations only capture relevant relations and abstract from unnecessary details. They are especially suited to handle uncertain or incomplete information. Exploiting the domain structure makes QSTR effective and efficient. One particular goal of QSTR is to reach for formal methods capable of human-level spatial and temporal reasoing. Thus, QSTR is relevant for human-machine interfaces, but QSTR can provide effective means for a variety of other applications as well. Within this talk, we review the essential QSTR reasoning techniques and evaluate how the state-of-the-art suits application requirements. We argue for the need of reference implementations and present the toolbox SparQ developed in our project. With our research and the development of SparQ we aim for making applications benefit from QSTR. Dr. Diedrich Wolter is principal investigator of the project qualitative reasoning about paths, shapes, and configurations at the University Bremen in the framework of the interdisciplinary Transregional Collaborative Research Center Spatial Cognition: Reasoning, Action, Interaction. The project develops qualitative representations and reasoning methods for high-level agent control.
The IBM Ph.D. Fellowship Program is an intensely competitive worldwide program, which honors exceptional Ph.D. students who have an interest in solving problems of interest to IBM and which are fundamental to innovation in many academic disciplines and areas of study. These include: computer science and engineering, electrical and mechanical engineering , physical sciences (including chemistry, material sciences, and physics), mathematical sciences (including optimization), business sciences (including financial services, communication, and learning/knowledge), and service sciences, management, and engineering (SSME).
Einblicke in die Entwicklung des Windows-Betriebssystems haben alle erhalten, die am Mittwoch, 21. Oktober, an der TUHH den Vortrag des Senior Vice President von Microsoft, Jon DeVaan, verfolgten. Der Chefentwickler, ein studierter Mathematiker und Informatiker, erläuterte vor einer interessierten Zuhörerschaft im Raum 2022 die Kunst des Projektmanagements am Beispiel der Entwicklung von Windows 7. Etwa 1000 Microsoft-Mitarbeiter, hauptsächlich in den USA und Indien, sind an der Entwicklung dieses komplexen Systems beteiligt gewesen, die in drei Phasen verläuft, die sich solange wiederholen, bis das Produkt fertig ist: In der ersten Stufe arbeiten Gruppen bis zu 40 Mitarbeitern an den einzelnen Säulen der zukünftigen Software, danach findet in der zweiten Phase die Qualitätsprüfung bei der Integration der Säulen statt, und am Ende steht das Softwareprodukt. Anschließend werden diese Phasen wiederholt udn dadurch das Produkt immer weiter verfeinert. Plan the work und work the plan!, sei das Leitmotto, sagte DeVaan. Dabei wurde auch betont, welche Bedeutung Microsoft heute dem Thema Sicherheit und dem Security Development Lifecycle beimisst.
Computer-Aided Engineering und insbesondere numerische Simulationen sind ein wesentlicher Bestandteil der modernen Produktentwicklung. Für Produkte, die ein hohes Maß an Zuverlässigkeit und Robustheit erfordern, ist die Vorhersage der Auswirkungen produktions- und einsatzbedingter Unsicherheiten von großer Bedeutung. Zu diesem Zweck wird in wachsendem Maße Stochastische Simulation eingesetzt. Die Auswertung der umfangreichen stochastischen Simulationsergebnisse stellt den Ingenieur jedoch vor ein methodisches Problem, da die verfügbaren Methoden der statistischen Datenvisualisierung und der wissenschaftlichen Visualisierung nur begrenzt geeignet sind.
Im Rahmen des Vortrags werden daher neuartige Methoden zur Visualisierung und systematischen Analyse stochastischer Simulationsergebnisse von zeitlich und geometrisch diskretisierten Modellen aufgezeigt. Anschließend wird das Potential der Visualisierungsmethoden an exemplarischen Anwendungsfällen demonstriert.
Conceptual data models play a major role in Computer Science as large-scale agent systems are designed such that computational entities can migrate over the web, can interact, and can contact world-wide information repositories. In these contexts a shared understanding between agents based on formalized conceptual data models (ontologies) is mandatory. In particular, it must be accepted that none of the agents has (or can obtain) complete information about the world. Thus, query answering with respect to ontologies and incomplete information becomes more and more important. In addition, modules have to be defined such that information can be sensibly shared and reasoned upon. Many research activities in the world manifest the importance of this research field, and joint acitivities have to be started to further clarify the relation between advanced database systems and practical knowledge representation and reasoning systems.
The Institute for Software Systems (STS) at Hamburg University of Technology invites two leading experts in this field, Alex Borgida (USA) and Volker Haarslev (Canada). They will give presentations about parts of their work in the above-mentioned research area. The two presentations will be complemented with a presentation about our work at STS. Talks will be given in a special colloquium at STS, with which we would like to encourage research collaborations in Computer Science between Hamburg University of Technology (as well as other universities in Hamburg) and well-known institutes and groups in the world.
The presentations are described below:
It is argued that, given an ontology (or a program for that matter), there is a difference between partitioning it into 'modules' and importing information about some set of identifiers defined in it. We start by surveying a sample of lesser known papers on this topic in both the AI and Database literature. Based on this, we derive a list of desirable properties for the notion of 'importing a set of identifiers from an exporting to an importing knowledge base', and provide a framework for alternate formal definitions of this notion. The best-known proposal starts from the logical notion of 'conservative extension' [Cuenca Grau et al] but is dependent on the syntactic formulation of the ontology. Our proposal suggests conceptually expanding the ontology ( adding trivial inferences, making it more 'fine-grained' [Horridge et al], etc.) and allowing limitations on the use of imported terms. We also discuss the difficulties of minimizing the number of concepts rather than the number of axioms during importing.
In this talk I will briefly introduce description logics / OWL-DL and associated inferences services. Afterward I will discuss the architecture of the description logic reasoner Racer and highlight selected tableau optimization techniques, especially on assertional reasoning. Several recently devised optimization techniques were introduced due to requirements from semantic web applications relating huge amounts of (incomplete) data to ontological information.
Terabytes of data will be a common size to be managed on personal computers in the not too far future, and database technology has matured in such a way that this amount of data is manageable to a large extent even if queries are defined in an ad hoc manner. In particular, a common assumption in database applications is that the conceptual schema is used for deriving the implementation schema (e.g., relational schema), which is then used for storing data. Views might relate notions from the conceptual to the implementation schema, and if updates are neglected, views can easily be used to manage a database with respect to the conceptual schema. In almost all practical database systems, data is considered to be complete, with a corresponding impact on query answering. In new application contexts such as the semantic web, however, software agents migrate to new sites, and they use their conceptual schema for querying large data repositories found at different sites. With new schemata being used, data can hardly be seen as complete, and thus, query answering w.r.t. incomplete information becomes more and more important. Using ontologies, query answering with respect to views and incomplete data descriptions becomes possible. In the tutorial we present recent advances in query answering techniques for for large sets of data descriptions w.r.t. large and expressive ontologies (large sets of axioms specified in an expressive language) under the assumption that data descriptions are assumed to be incomplete. We present query languages which can be practically used in combination with ontologies of varying expressiveness.
We would like to thank Joachim Schmidt and Resa Rasouli for providing pictures of the event.
If somebody shown on these pictures would like to have the corresponding pictures removed, please send an email to r.f.moeller --at-- tu-harburg.de.