phyllis@utcsrgv.UUCP (Phyllis Eve Bregman) (05/17/84)
[****] UofT Department of Computer Science Seminar Schedule for the week of May 14th, 1984 May 17th, 4:00 P.M., GB244, Jeffrey Zucker, SUNY: "Program correctness over abstract data structures, with error-state semantics". ABSTRACT: We extend the classical work on program correctness for Hoare-style proof systems in two ways: (a) We consider programs over not just integers, but abstract data structures; in fact over classes of many-sorted structures of a given signature, one sort of which will be numerical. In the case of programs with recursive procedures, proof of expressivity of the assertion language requires an investigation of computability over abstract structures. (b) The semantics are designed so as to model errors arising from uninitialized variables. If such a variable is called in the course of a computation, the computation will halt in an "error state". Similarly, any expression containing such a variable may, on evaluation, yield the "unspecified value". In particular, considering Boolean expressions, we are led to a three-valued logic. -- Phyllis Eve Bregman CSRG, Univ. of Toronto {decvax,linus,ihnp4,uw-beaver,allegra,utzoo}!utcsrgv!phyllis CSNET: phyllis@toronto (416) 978 6985