September 20 – 24 , 1993, Dagstuhl Seminar 9338

Non-Classical Logics in Computer Science


V. Marek, A. Nerode, P.H. Schmitt

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Dagstuhl's Impact: Documents available
Dagstuhl-Seminar-Report 73


During the last ten, fifteen years we could witness a remarkable revival of interest in non-classical logics foremost in connection with topics from computer science. There seem to be two explanations for this phenomenon:

  • The intention to use non-classical logics, like many-valued, modal or temporal logics for real world applications has made the usual reductions to classical first-order logic less attractive, since they obscure the intuitive meaning of formulas. Also the implementations of theorem provers for these logics seem to work more efficient without first translating them.
  • Computer science also brought about a change in the focus of application areas of logic, from mathematics to the representation of and reasoning with more general and less structured domains of knowledge. This led to the invention of new types of logic. Non-monotonic logic is the prime example to be named here.

To provide the necessary focus for a fruitful interaction during the seminar we limited the contributions to the following subjects:

  • non-monotonic logics to model common sense reasoning,
  • Horn-clause logic and its extensions as a basis for declarative programming and as a source of non-monotonic inference,
  • many-valued logics to extend the expressiveness of first-order logic and as a frame for explaining phenomena arising in two-valued logic and modal logics as a basis for treating temporal and epistemological aspects

The bulk of the talks turned out to be on the subject of non-monotonic logic, which can rightly be judged to have turned into a mature subject with a sound theoretical basis and moving towards serious implementations and applications. Despite the seemingly non-homogeneous audience but supported by the known interactions between modal and non-monotonic logic and also between many-valued logic and semantics of logic programs intensive and stimulating conversations evolved during the week of the seminar and will, it is to be hoped, further continue.


In the series Dagstuhl Reports each Dagstuhl Seminar and Dagstuhl Perspectives Workshop is documented. The seminar organizers, in cooperation with the collector, prepare a report that includes contributions from the participants' talks together with a summary of the seminar.


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