Properties of Slicing Definitions

Weiser's original papers on slicing defined the concept in an informal way. Since then there have been several attempts to formalise slicing using various formal methods and semantics of programs. In this paper we start by defining some properties that a definition of slicing might reasonably be expected to satisfy and then compare different definitions of slicing to see which properties are satisfied. Properties are classified into "floor" requirements: all slices satisfying the property must be considered as valid, and "ceiling" requirements: slices which do not satisfy the property must not be considered valid. Any slicing relation which lies above a "floor" requirement, or below a "ceiling" requirement, satisfies the property in question. The main result of the paper is the proof that, given a certain property of the programming language (informally: it is possible to write an infinite loop in the language), two of the most basic and fundamental properties of slicing are sufficient to completely characterise the semantic part of the slicing relation. These properties are: behaviour preservation and truncation.