Invited Talks

- BCTCS 2007: British Colloquium for Theoretical Computer Science, Oxford, April 2007.

- British Logic Colloquium, Oxford, September 2007.

- ODSA 2006: Optimal Discrete Structures and Algorithms, Rostock (Germany), September 04 - 06, 2006

- BNCOD 2006: 23rd British National Conference on Databases Queen's University Belfast, Northern Ireland, July 18- 20, 2006.

- MathCSP 2006: International Workshop on Mathematics of Constraint Satisfaction: Algebra, Logic and Graph Theory. St. Anne's College, University of Oxford, March 20-24, 2006.

- Information Sciences of New Era: Brain, Mind and Society, Sendai, Japan, Sept. 26-27, 2005.

- WG 2005: 31st International Workshop on Graph-Theoretic Concepts in Computer Science, Metz, France, June 23-25, 2005.

- BTW 2005: 12th Conference of the German Computer Science Society on Database Systems for Business, Technology, and the Web ( 12. GI-Fachtagung Datenbanksysteme für Business, Technologie und Web), Karlsruhe, Germany, Winter 2005.

- IJCAR 2004: International Joint Conference on Automated Reasoning. Cork, Ireland, July 4-8, 2004.

- 23 ACM SIGMOD-SIGACT- SIGART Symposium on Principles of Database Systems (PODS 2004) Paris, France - June 14-16, 2004

- Third International Symposium on Foundations of Information and Knowledge Systems (FoIKS 2004), Vienna (Austria), February 17 - 20, 2004.

- IEEE/WIC International Conferences on Web Intelligence and Intelligent Agent Technology, (WI/IAT-03), Halifax, Canada, Oct. 13-16, 2003.

- LICS 2002, IEEE Symposium on Logic in Computer Science, Copenhagen, Denmark, July 2002.

- Logics in Artificial Intelligence JELIA'02, Calabria, Italy, September 2002.

- Ninth International Workshop on Nonmonotonic Reasoning NMR 2002, Toulouse, France, April 2002.

- Symposium on the Effectiveness of Logic in Computer Science (ELICS), Saarbruecken, Germany, March 4-6, 2002.

- Invited system demo and paper at Intern. Workshop on Logic Programming and Nonmonotonic Reasoning (LPNMR), Vienna, 2001.

- 26th International Symposium on Mathematical Foundations of Computer Science (MFCS'01), Mariánské Lázne, CFR, 2001.

- 5th International Conference on Developments in Language Theory (DLT'01), Vienna, July 16-21, 2001.

- 7th International Conference on Logic Programming and Automated Reasoning (LPAR 2000), Reunion Island, Frankreich, November 2000.

- DEXA'99 Database and Expert Systems Applications, Florence, Italy, August/September 1999

- International Symposium on Knowledge Representation and Reasoning (KR'96), Cambridge, MA, Nov. 1996.

- 11th International Logic Programming Symposium (ILPS), Ithaca, NY, 1994.

- Logics in Artificial Intelligence JELIA'94, York, UK, 1994.

- 12th International Conference on Fundamentals of Computation Theory, (FCT'97), Krakow, September 1997.

- Second Intern. Workshop on Logic Programming and Nonmonotonic Reasoning (LPNMR), Lisbon, 1993.

- International Symposium on Mathematical Foundations of Computer Science (MFCS), Prague, 1995.

- International Summer School on Logic Programming, Alghero, Italy, June 1996.

- Conference on Inductive Logic programming (ILP'97), Prague, September 1997.

- Italian Artificial Intelligence Conference 1997, Rome, Sept. 1997.

- LLC'99 Third International Symposium on Language, Logic and Computation, Batumi, Georgia, September 1999.

- Workshop on Proof Theory, Complexity and Meta-mathematics, Kurt Gödel Society, Vienna, April 1994.

- European Conference on Computer Assisted Systems Theory (EUROCAST), Innsbruck, 1995.

- First COMPULOG Net Meeting on Knowledge Bases, Munich, 1992.

- Logic Colloquium 95, Haifa, Israel, 1995. Workshop on Nonmonotonic Reasoning.

- Finite Model Theory Workshop, Oberwolfach, Germany, 1998.

- Workshop on Finite Model Theory and Implicit Complexity, at FLOC'99, Trento, July 1999.

Other Invitations and visits.

Over 120 talks at different european and US universities or research institutions (which are not listed in detail). Research and teaching activity at a number of different universities, e.g. Stanford University (overall 9 month), UNAM Mexico (intensive course, 1 week), ETH Zürich (sabbatical), UC Berkeley (visiting professor), Paris VII (visiting professor).