Research Group on the Foundations of Artificial Intelligence

Contact

Dr. Stefan Wölfl is member of the Research Group on the Foundations of Artificial Intelligence at the University of Freiburg since April 2003. Currently he is working on the SFB/TR 8-project Constraint-Based Reasoning in Qualitative Spatio-Temporal Calculi (LogoSpace).

Read more ...

Research Interests

• Constraint based spatial and temporal reasoning
• Action theory and multi-agent systems
• Modal and temporal logics
• Ontology, ontologies, and description logics
• Algebraic specification and formal verification
• Model checking

Recent Publications

(Show all abstracts) (Hide all abstracts)

• Matthias Westphal and Stefan Wölfl.
  Bipath Consistency Revisited.
  In Proceedings of the ECAI'08 Workshop on Spatial and Temporal Reasoning. Patras, Greece 2008.
  (Show abstract) (Hide abstract) (PDF)
  

  In the field of qualitative spatial and temporal reasoning combinations of constraint calculi have attracted considerable research interest in recent years. Beside combinations of spatial and temporal calculi, it is an important research topic to develop generic methods for combining calculi dealing with different spatial aspects. The prototypical example is the combination of the region connection calculus RCC8 and the point algebra first discussed by Gerevini and Renz, which allows to represent, and reason about, topological and size information about spatially extended objects. To solve constraints in this calculus, Gerevini and Renz also proposed an algorithm, the bipath consistency algorithm, which allows for deciding consistency of a given constraint network for specific sets of relations combining topology and size. In this article we will compare the "bipath consistency"-based combination method to the standard method, which is to combine calculi by generating a new calculus and applying the standard path consistency method. Gerevini and Renz's calculus combining topological and size information will serve as the running example of such combinations and also as a test case for an empirical analysis.

• Zeno Gantner, Matthias Westphal and Stefan Wölfl.
  GQR - A Fast Reasoner for Binary Qualitative Constraint Calculi.
  In Proceedings of the AAAI'08 Workshop on Spatial and Temporal Reasoning. Chicago, USA 2008.
  (Show abstract) (Hide abstract) (PDF)
  

  GQR (Generic Qualitative Reasoner) is a solver for binary qualitative constraint networks. GQR takes a calculus description and one or more constraint networks as input, and tries to solve the networks using the path consistency method and (heuristic) backtracking. In contrast to specialized reasoners, it offers reasoning services for different qualitative calculi, which means that these calculi are not hard-coded into the reasoner. Currently, GQR supports arbitrary binary constraint calculi developed for spatial and temporal reasoning, such as calculi from the RCC family, the intersection calculi, Allen's interval algebra, cardinal direction calculi, and calculi from the OPRA family. New calculi can be added to the system by specifications in a simple text format or in an XML file format. The tool is designed and implemented with genericity and extensibility in mind, while preserving efficiency and scalability. The user can choose between different data structures and heuristics, and new ones can be easily added to the object-oriented framework. GQR is free software distributed under the terms of the GNU General Public License.

• Stefan Wölfl, Till Mossakowski and Lutz Schröder.
  Qualitative constraint calculi: Heterogeneous verification of composition tables.
  In Proceedings of the Twentieth International Florida Artificial Intelligence Research Society Conference (FLAIRS 2007), pp. 665-670. AAAI Press 2007.
  

• Diedrich Wolter, Frank Dylla, Lutz Frommberger, Jan Oliver Wallgrün, Bernhard Nebel and Stefan Wölfl.
  Qualitative Spatial Reasoning for Rule Compliant Agent Navigation.
  In Proceedings of the Twentieth International Florida Artificial Intelligence Research Society Conference (FLAIRS 2007), pp. 673-674. AAAI Press 2007.
  

• Frank Dylla, Lutz Frommberger, Jan Oliver Wallgrün, Diedrich Wolter, Berhard Nebel and Stefan Wölfl.
  SailAway: Formalizing navigation rules.
  In Proceedings of the Artificial and Ambient Intelligence Symposium on Spatial Reasoning and Communication (AISB 2007). 2007.
  

• Till Mossakowski, Lutz Schroeder and Stefan Wölfl.
  A categorical perspective on qualitative constraint calculi.
  In Qualitative Constraint Calculi - Application and Integration, Workshop at KI 2006. 2006.
  

Read more ...