and

A slice is constructed by deleting statements from a program whilst preserving some projection of its semantics. Since Mark Weiser introduced program slicing in 1979, a wide variety of slicing paradigms have been proposed, each of which is based upon a new formulation of the slicing criterion, capturing the semantic projection to be preserved during the process of command deletion. This paper surveys these slicing criteria, attempting to establish a set of parameters which combine to form a slicing criterion. The effort to abstract a general set of parameters for slicing criteria highlights the existence of many new possibilities for slicing, corresponding to, as yet unpublished, criteria. Many of these novel slicing criteria may find applications in program comprehension and analysis. The paper introduces no new algorithms for constructing slices, rather it introduces new criteria with respect to which slices might usefully be constructed. The paper also goes some way towards a unification of previous, apparently different, but related, approaches to slicing in which the process of command deletion remains invariant while the semantic projections preserved during the command deletion process vary