The Object Constraint Language is a textual specification language which forms part of the Unified Modelling Language[8]. Its principal uses are specifying constraints such as well-formedness conditions (e.g. in the definition of UML itself) and specifying contracts between parts of a system being modelled in UML. Focusing on the latter, we propose a systematic way to extend OCL with temporal constructs in order to express richer contracts. Our approach is based on observational mu-calculus, a two-level temporal logic in which temporal features at the higher level interact cleanly with a domain specific logic at the lower level. Using OCL as the lower level logic, we achieve much improved expressiveness in a modular way. We present a unified view of invariants and pre/post conditions, and we show how the framework can be used to permit the specification of liveness properties.

For purposes of security analysis, cryptographic protocols can be translated from a high-level message-list language like CAPSL into a multiset rewriting (MSR) rule language like CIL. The natural translation creates two rules per message or computational action. We show how to optimize the natural rule set by about 50% into a form similar to the result of hand encoding, and prove that the transformation is sound because it is attack-preserving, and unique because it is terminating and confluent. The optimization has been implemented in Java.0-7695-0671-2/00 $10.00 ã 2000 IEEE

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