Behavioral semantics of nonrecursive control structures

Abstract

Knowledge Based Programming is programming in an environment which has substantial knowledge of the semantic domain for which the programs are being written and of the purposes that the programs are supposed to satisfy. Actors are a semantic concept in which no active process is ever allowed to treat anything as an object; instead a polite request must be extended to accomplish what the activator desires. Using actors the PLANNER Project is constructing a Programming Apprentice to make it easier for expert programmers to do knowledge based programming. The apprentice is to aid in establishing and maintaining consistency of specifications, validating that modules meet their specifications, answering questions about behavioral dependencies between modules, and analyzing the implications of perturbations in modules and their specifications.

In The course of this research we have found that we needed to make use of non-recursive control structures and to be able to rigorously formulate their semantics. Our semantics is a generalization of the mathematical semantics of Sco Scott for junctions. Thus it differs from the operational semantic models [such as the CONTOUR model and the Bobrow-Wegbreit mode] that have been proposed which are formulated in terms of operations on activation records. This paper reports some preliminary results and tentative conclusions.