Research & Interests

Projects & Project Involvements

04/2013 - today
SRI International:
I am a computer scientist in the Artificial Intelligence Center, working on various SRI projects.
10/2010 - 04/2013
SRI International:
I am a computer scientist in the Artificial Intelligence Center working on project HALO.
I was mainly involved with supporting the knowledge entry backend, but also worked on question answering algorithms.
2009 - 10/2010
A project funded by the European Commission, see a stream-based cognitive architecture for multimedia interpretation.
2009 - 2010
A project funded by the German Research Foundation (DFG), see a cognitive architecture for the interpretation of multimedia streams.
This was a joint effort with the CASAM project above.
2008 - 2010
Work on the W3C Member Submissions OWLlink. I specified the functional binding and the S-Expression binding in collaboration with the company Derivo, colleagues from the university of Ulm, and DOCOMO Euro Labs.
My Common Lisp open source framework OntoLisp provides the native reference implementation of OWLlink.
2008 - 2009
A project funded by the European Commission on semantic multi-media interpretation and ontology bootstrapping. My ontology query language "nRQL" was extended with abductive query answering capabilities to provide the reasoning backbone of the semantic interpretation engine.
2007 - 2009
Consultant for DOCOMO Euro Labs:
DL-based complex ontology-based event recognition for the DOCOMO projects "ContextWatcher" and "IYOUIT".
2007 - 2010
A termination-safe scripting and extension language for the RacerPro server.
See this Soduko solver written in MiniLisp and this slides for explanation (pages 28 - 32).
2001 - 2006 (PhD Work)
DLMAPS (Description Logic Maps):
An experimental, prototypical description logic-based geographic information system, featuring a high-performance deductive query answering engine. The framework supports hybrid (spatial and logical) representations and is capable of processing ontology-based spatio-thematic queries.
The Racer query language nRQL is an instantiation of this generic query engine framework.
Similar systems have appeared, e.g. "Pellet Spatial" ™ by Clark & Parsia, and standards such as GeoSPARQL are emerging.
A Tangram-playing Lisp Program:
This was implemented in CLIM in Lispworks and demonstrates heuristic spatial search to solve geometric tiling problems.
2003 - 2010
nRQL (new Racer Query Language):
An influential Description Logic and OWL query language for the RacerPro reasoner. The generic query engine underlying nRQL explored the idea of representation- and application-specific entailment relationships (nowadays called "entailment regimes" in SPARQL), offering expressive means such as classical negation and negation as failure, universal quantification, subqueries, user-defined procedural extensions, etc. Many of these expressive means have been adopted for standards such as SPARQL in the meantime.
nRQL was the first practical, fully working description logic "ABox" query engine with a heuristic cost-based query optimizer. The optimizer uses selectivity heuristics for re-ordering of subgoals in conjunctive queries, hence generating effective query evaluation plans by rewriting queries.
The optimizer was fully operational and documented in RacerPro in 2004. More details about the optimizer can by found in my thesis from 2007, together with a comprehensive evaluation of the effectiveness of the various optimization techniques using the LUBM benchmark. Some of these optimization techniques have been applied to SPARQL by other researchers in the meantime, for example, see this paper by Stocker et al., or this paper by Glimm et al.
In 2004, nRQL became the first OWL query engine that could answer the queries from the (nowadays standard) "Lehigh University Benchmark (LUBM)" completely.
Here is a (non-exclusive) list of researchers who have used nRQL in their projects: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11
2004 - 2010
RacerPorter (for Racer Systems GmbH):
A GUI / IDE for RacerPro. You can see RacerPorter & RacerPro in this YouTube video published by Franz Inc, which used to be a partner company of Racer Systems GmbH & Co. KG.
1997 - 1998 (Diploma Thesis)
An experimental visual spatial query language and prototype system for geographic information systems, applied to digital city maps. The VISCO spatial query processing engine featured a cost-based heuristic spatial optimizer, similar to the nRQL engine later (see pages 165 - 180). Perhaps you will enjoy our QuickTime movie ;-)
1995 - 1996 (Project Work)
A description logic-based graphical editor for designing visual formalisms (e.g. Petri Nets). The editor is capable of recognizing spatial constellations described by spatial concepts in a description logic ontology. Enjoy our QuickTime video ;-)