Intersections of Sets and Bags of Extended Substructures, and Can Bag Comprehension be Used at All?

Formal specifications that exhibit similarities will often have similar solutions. Thus, it is useful to construct generalized specifications that describe classes of problems, since (partial) solutions to the generalized problem can be used for obtaining solutions for the specific problems. In this paper we study a class of generalized pattern matching problems, in which the essential operation is the intersection of a particular set and a bag of extended substructures of a structured object. We present a formalization of bags of extended substructures and define the ISBES (Intersection of Sets and Bags of Extended Substructures) class of problems. Some example ISBES specifications are shown, and we present some first ideas about applicable program transformation strategies for ISBES problems. The second paper discusses conditions under which the non-standard specification mechanism of a bag comprehension may be safely used. The first paper has been published (/pubs/1991/161/) and included in my PhD thesis.