Specifying Reusable Components

Reusable software components need expressive specifications. This paper outlines a rigorous foundation of model-based contracts, a method to equip classes with strong contracts that support accurate design, implementation, and formal verification of reusable components. Model-based contracts conservatively extend the classic Design by Contract approach with a notion of model, which underpins the precise definitions of such concepts as abstract object equivalence and specification completeness. Experiments applying model-based contracts to libraries of data structures suggest that the method enables accurate specification of practical software.