State constraints and pathwise decomposition of programs

A state constraint is a programming construct designed to restrict a program's domain of definition. It can be used to decompose a program pathwise, i.e. dividing the program into subprograms along the control flow, as opposed to dividing the program across the control flow when the program is decomposed into functions and procedures. As a result, a program consisting of one or more execution paths of another program can be constructed and manipulated. The author describes the idea involved, examines the properties of state constraints, establishes a formal basis for pathwise decomposition and discusses their uses in program simplification, testing and verification.<
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