Temporal Semantics of Meta-Level Architectures for Dynamic Control of Reasoning

In the literature on meta-level architectures and reflection two separate streams can be distinguished: a logical stream (e.g., [Bowen and Kowalski, 1982], [Giunchiglia et al., 1993], [Weyhrauch, 1980]) and a procedural stream (e.g., [Clancey and Bock, 1988], [Davis, 1980]). Unfortunately there is a serious gap between the two streams. In the logical stream one restricts oneself often to static reflections; i.e., of facts the truth of which does not change during the reasoning: e.g., provable(A) (with A an object-level formula). In the procedural stream usually facts are reflected the truth of which changes during the whole reasoning pattern; e.g. control statements like currentgoal(A) with A an object-level formula, that are sometimes true and sometimes false during the reasoning. If applications to dynamic control of complex reasoning tasks are concerned these dynamic reflections are much more powerful (for applications see, e.g. [Davis, 1980], [Clancey and Bock, 1988], or [Brumsen et al., 1992], [Geelen and Kowalczyk, 1992], [Tan and Treur, 1992a1, [Tan and Treur, 1992b], [Treur, 1991a], [Treur and Veerkamp, 1992]). However, a logical basis for this is still lacking. The current paper provides a logical foundation (based on temporal logic) of meta-level architectures for dynamic control. Our logical framework enables one to study these dynamic meta-level architectures by logical means. It can be viewed as a contribution to bridge the gap between the logical stream and the procedural stream.