We demonstrate that modules support component oriented specification and verification techniques in the presence of object identity. Also, modules allow for extending the notion of compatibility to groups of classes. This discussion is presented in Section 6. One approach to overcome this problem is to restrict the usage of object identities. We introduce modules into the specification of object oriented systems.
Modules provide a precise interface to the outside world.
Inside modules, object identities can be used without restrictions. However , if object identities are used in invariants specifying a system, they may not refer to objects beyond the module s border. Springer Verlag, 1991. Incremental Program Validation. This is obviously the right way to go.