Formal Semantics of OCL Messages

The latest OCL 2.0 proposal provides two semantic descriptions, i.e., a metamodelbased semantics that uses UML itself to associate the semantic domain with the language concepts and a formal semantics based on a set-theoretic approach called object model. Unfortunately, these two semantics are currently neither consistent nor complete, as (a) the formal semantics does not consider the newly introduced concept of OCL messages and (b) both semantics lack an integration of Statecharts and a semantic definition of state-related operations. This article focuses on a formal semantics for OCL messages as a foundation for consistency among the two OCL semantics. We extend object models and present an extended definition of a system state that comprises all relevant information to be able to evaluate OCL expressions also w.r.t. OCL messages.