An incremental approach to local equality predicates in OBJ specification languages

Abstract

OBJ algebraic specification languages support automated equational reasoning based on term rewriting for interactive verification. The equational reasoning is sound but not always complete in general. In our previous work, we have given a condition for sound and complete equational reasoning for OBJ specifications and have proposed the notion of local equality predicates (LEP), which is not only used for verification but also used for description of specifications. In this study, we propose a method to prove termination and confluence of specifications with LEPs. Termination and confluence are important properties of term rewriting and are parts of the LEP condition. By using the proposed method, we can use nested LEPs for large and complex modules.