It is often claimed that strengths of object-oriented approaches include the integration of data and process perspectives, opportunities for reuse, and high comprehensibility. In this paper focus is on object-oriented analysis, and the core models of an object oriented analysis method are examined, formalized, and enhanced to define a general framework. Jacobson's Objectory method is used as a starting point because of its underlying philosophy and its succesful application in practice. Core models are the object-oriented data model and the communication model, which is an integration of the interaction and the behaviour model. As Objectory emphasizes interaction between objects, the paper focuses solely on the latter model. The communication model is extended with constructs to specify parallelism within an object, synchronization of concurrent execution paths, and a basic mechanism to receive results from asynchronous service requests.