Item

Abstract

n this paper we study possibilities of reasoning about functions over theories of data types which satisfy certain recursion (or homomorphism) properties, with a focus on emphasizing possibilities of hierarchical and modular reasoning in such extensions and combinations thereof. We start by considering theories of absolutely free data structures, and continue by studying extensions of such theories with selectors, with functions which attach scalar data to the data structures and with additional functions defined using a certain type of recursion axioms (possibly having values in a different -- e.g.\ numeric -- domain). We show that in these cases locality results can be established. This allows us to reduce the task of reasoning about the class of recursive functions we consider to reasoning in the underlying theory of absolutely free data structures (resp. in a combination of the theory of absolutely free data structures with the theory attached with the domains of the additional functions). We then show that similar results can be obtained if we relax some assumptions about the absolute freeness of the underlying theory of data types. We investigate the applications of these ideas in verification and cryptography.