Preserving Specific Properties in Programm Development: How to Debug Programs (Conference Version)

The problem of preserving specific temporal properties in program development is addressed. A new relation between programs, or, more generally, between specifications, is defined. This relation is parameterized by a (finite) collection of temporal properties which will be preserved by that relation. Such a relation will, in general, not preserve all temporal properties. It is proved, however, that for a particular choice of the parameter the new relation coincides with Abadi and Lamport's notion of implements [1], which preserves all (externally visible) temporal properties. As a consequence, the approach for program development proposed in the current paper is as least as powerful as those which use implements as their basic refinement relation. Examples of the latter approaches are those proposed by Back [4], by Lynch and Tuttle [27], and by Lam and Shankar [25]. It is argued that the approach in program development which preserves only certain temporal properties is preferable to those approaches which preserve all temporal properties.