Contract Soundness for Object-Oriented Languages

Checking pre- and post-conditions of procedures and methods at runtime helps improve software reliability. In the procedural world, pre- and post-conditions have a straightforward interpretation. If a procedure’s pre-condition doesn’t hold, the caller failed to establish the proper context. If a post-condition doesn’t hold, the procedure failed to compute the expected result. In the object-oriented world, checking pre- and post-conditions for methods, often called contracts in this context, posescomplex problems. Because methods may be overridden, it is not sufficient to check only pre- and post-conditions. In addition, the contract hierarchy must be checked to ensure that the contracts on overridden methods are properly related to the contracts on overriding methods. Otherwise, a class hierarchy may violate the substitution principle, that is, it may no longer be true that an instance of a class is substitutable for objects of the super-class. In this paper, we study the probl...

• Type: Conference
• Year: 2001
• Where: OOPSLA
• Authors: Robert Bruce Findler, Matthias Felleisen
• Keywords: Contract Enforcement, Contracts, Object-oriented World, OOPSLA 2001, Security Privacy