Reasoning About Multiple Related Abstractions With MultiStar

Encapsulated abstractions are fundamental in object-oriented programming. A single class may employ multiple abstractions to achieve its purpose. Such abstractions are often related and combined in disciplined ways. This paper explores ways to express, verify and rely on logical relationships between abstractions. It introduces two general specification mechanisms: export clauses for relating abstractions in individual classes, and axiom clauses for relating abstractions in a class and all its descendants. MultiStar, an automatic verification tool based on separation logic and abstract predicate families, implements these mechanisms in a multiple inheritance setting.