Program slicing can be used as a support for program comprehension, because it allows a large program to be divided up into smaller slices, each of which can be understood in isolation from the rest. As such, slicing facilitates the familiar approach of `divide and conquer'.

This paper surveys the existing slicing techniques for object-oriented programs. Many commercial objectoriented programs are concurrent in nature. Concurrency is typically implemented in the form of multithreading or message passing using sockets or both. We therefore review the available techniques in slicing of concurrent object-oriented programs. Another trend that is clearly visible in object-oriented programming is client-server programming in a distributed environment. We briefly review the existing techniques for slicing of distributed object-oriented programs.

One of the critiques on program slicing is that slices presented to the user are hard to understand. This is mainly related to the problem that slicing `dumps' the results onto the user without any explanation. This work will present an approach that can be used to `filter' slices. This approach basically introduces `barriers' which are not allowed to be passed during slice computation. An earlier filtering approach is chopping which is also extended to obey such a barrier. The barrier variants of slicing and chopping provide filtering possibilities for smaller slices and better comprehensibility. The concept of barriers is then applied to path conditions, which provide necessary conditions under which an influence between the source and target criterion exists. Barriers make those conditions more precise.

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Although Weiser originally defined a program slice to be an executable projection of a program, much of the research on slicing has focused on closure slices, which consist of the set of statements and conditions of the program that might affect the value of a given variable at a given statement or condition of interest. While closure slices can be useful, there are some contexts in which executable slices are preferable. Closure slices are not generally executable because there can be mismatches in the slice between the sets of actual parameters at different call-sites to a procedure p and the formal parameters ofp. This paper presents a new approach to creating executable slices. Our algorithm addresses the parameter-mismatch problem by creating specialized versions of procedures that have different sets of formal parameters. Moreover, the slice returned by the algorithm is minimal: the slice consists of the set of specialized procedures that solves a certain coarsest-partition problem. The paper presents solutions for some additional issues that arise with more realistic languages than considered in past work. It also presents the results of an experimental evaluation of the algorithm applied to C programs. 1.