Abstract
The paradigm of contractual specification provides a transparent way of specifying object-oriented systems. In this paradigm, system consistency is specified using so-called invariants. Runtime validation of invariants is a complex problem. Existing validation methods require either exhausting validation of an invariant for all objects of the corresponding class or the use of restrictive type systems. In this paper a non-exhaustive method of invariant validation is proposed. It is proved that the method is sound and an implementation of this method is discussed. It is shown also how to extract context free languages corresponding to OCL-invariants.