“…The study of invariant assertions, and more broadly the functional analysis of programs, have been the focus of active research in the seventies and eighties, and the subject of renewed interest in the last few years [1,6,7,9,20,23,37,39,40,61]. In this paper we wish to investigate the relationships between this well known, thoroughly researched, concept, and two distinct but related concepts: invariant functions [52] and invariant relations [50].…”