Temporal Reasoning and Default Logics.
YALE UNIV NEW HAVEN CT DEPT OF COMPUTER SCIENCE
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This document presents axioms to represent some simple concepts in temporal reasoning events occuring at points in time, facts holding true over time, events causing facts to begin, facts causing contradictory facts to cease, and facts tending to remain true unless explicitly forced to cease. To express this last notion the authors couch the axioms in a default logic they alternatively consider the logics of McDermott and Doyle, of Reiter, and of McCarthy. This document defines precisely through a computer program and its formal description the conclusions its authors intend be drawn from these axioms, given a particular temporal state of affairs. They prove, however, that these conclusions are not deductions licensed by any of the above default logics. Further analysis leads to the conclusion that these logics are inherently incapable of representing this particular kind of default reasoning. Author