This is a description on a trip to Germany from 11 Sept to 2 October 2004, an edited version of a report written for the SEEK (Science Environment for Ecological Knowledge) project, which partially supported the trip. Sites visited included the Universities of Bremen, Dresden, and Leipzig, and Schloss Dagstuhl (the German computer science meeting center). Mainly, I presented work in the paper Data, Schema, and Ontology Integration, which was originally prepared for the Workshop on Combinations of Logic (CombLog'04), 28-30 July 2004, in Lisbon. This paper introduces the integration stack, consisting of data, schema, ontology, and ontology language, each of which requires translation for some cases of integration; it also summarizes work on our SCIA matching tool, and on the mathematical theory behind the integration stack and the tool, including general definitions for schema and schema mapping that encompasses spreadsheets, relational, XML, etc., as well as ontologies of different kinds (OWL, RDF, KIF, etc.); see our data integration page for more detail.
The Bremen Institute for Safe Systems subgroups headed by Prof Bernd Krieg-Bruckner on Cognitive Robotics and Formal Methods are involved in fascinating projects that include safe software, and navigation and control of a voice activated wheel chair. It seems that the different components rely on different logics, so that there is a need for integrating theories over different logics, which is being addressed using the theory of institutions, mainly by Dr Till Mossakowski, whose heterogeneous tool set is very impressive. I am hoping that an invitation to spend a month there next summer can be arranged, so I can learn more about these projects, perhaps help out a bit, and also collaborate further with Dr Mossakowski on the theory of institutions, particularly our ideas on Lindenbaum algebras. (Not to mention enjoy the elegance of the city of Bremen and the kindness of its inhabitants.)
Our second stop was the Workshop on Algorithms and Tools for Coinductive Reasoning, at the Technical University of Dresden, from 17 to 22 September 2004 (though we only attended 17 to 20), ably organized by Prof Horst Reichel. I presented the paper Behavioral Verification of Distributed Concurrent Systems with BOBJ, of which Kai Lin is a coauthor; this was originally a keynote lecture for the Conference on Quality Software, Dallas Texas, 5-6 November 2003, and it appears in the Proceedings (IEEE Press, 2003, pages 216-235); the slides are also available. This paper proves correctness of the alternating bit protocol making strong use of recent features of BOBJ, especially conditional circular coinductive rewriting with case analysis. It was delightful to spend some time with Grigore Rosu again, as well as with Prof Reichel and Till Mossakowski, and Dresden is an interesting city to visit, with its historic (but reconstructed) old center and scenic Elbe River, up which we sailed in a 100 year old steam boat, to the lovely village of Miessen for lunch. We also attended a very nice concert by the Dresden Philharmonic.
Our next stop was the Dagstuhl Seminar on Semantic Interoperability and Integration, from 20 to 24 September 2004, capably organized by Yannis Kafoglou, Marco Schorlemmer, Steffan Staab, and Michael Uschold. There were many interesting lectures and hardworking groups, involving participants from a great diversity of backgrounds. It seems that one of the official recommendations from the workshop will be to study foundations of information integration using the theory of institutions to formalize the notions of logic, theory over a logic, and translations of theories and logics. My lecture was "An Anthropology of a Science Lab," but most of my remarks in working groups were drawn from a paper on the institutional approach to ontology integration, Information Integration in Institutions, which shows how the information flow and channel algebra of Barwise and Seligman and the Formal Concept Analysis of Ganter and Wille can be done over any logical system, in a much more general way, and it also shows how many proposed notions of information integration are special cases of the category theoretic notion of co-relation, and gives some theorems about co-relations and integration. It was discussed quite a lot at Dagstuhl, and the IEEE Standard Upper Ontology project has also decided to adopt this approach as a basis for future work; see the working paper Logical Environments, by Robert Kent. My contributions to the seminar are summarized in the paper Three Perspectives on Information Integration, which is in preparation for the workshop proceedings.
In addition, my wife Ryoko gave a recital of her own compositions in the beautiful music room of the castle, which was well received by about 30 seminar attendees. We also had amazing accommodation in the old castle. Since we arrived a day late, I think perhaps they ran out of double rooms, and had to put us in the "Royal suite," three rooms, with a secret staircase to the music room, situated directly above our entrance room, with its huge castle front door.
In Leipzig, I attended many meetings with Prof Erhard Rahm, who is one of the leaders in tool building for database schema integration, and his students - these people work hard! - discussing database integration, schemas, ontologies, mappings, etc. Prof Rahm expects to adopt some ideas from our SCIA tool for the next generation of his COMA schema matching tool (it is called COMA++), especially our idea of critical points. Leipzig is a beautiful city, with a fascinating history that includes 20 years in which Johann Sebastian Bach lived and worked there, and the seeds of the movement that overthrew the old communist government, in the Nicholas Church (where Bach also performed every Sunday). We attended a lovely concert in the new Gewandhaus building with Prof Rahm, and fell in love with an old coffee house that features a giant brass elephant head over its door. Since Ryoko is a great fan of Bach, she was excited to see the Bach Museum, the Thomas Church, and other sites associated with that great composer; we also bought some Bach scores and souvenirs.
Finally, we returned to Bremen for one night, to catch our flight home the next morning; we were able to connect again with Till Mossakowski, to work some more on our project, "What is a Logic?".
An unusual feature of this trip was that it required us to travel between the Eastern and Western parts of Germany four times! We did this by train, and it was fascinating to notice the differences: Even today there are many abandoned factories in the East and some abandoned farms; there are many retired people and unemployed young people; prices are significantly lower; and life is a little slower for most people.
I hope to be able to add some photos to this page soon.