Coherent models

The OMT object model, however, only captures the static structure of the system. To model the dynamic and functional aspects, the object model is augmented with a dynamic model, which is given by state diagrams, and a functional model, which is handled by data flow diagrams. From a formal point of view this solution is rather unsatisfactory since, as argued in  [Hayes91], it is hard to establish the consistency of the combined model, consisting of an object, dynamic and functional model.

Model criteria -- formal approach


slide: Coherent models -- criteria

Consistency checking, or at least the possibility to do so, is important to increase our belief in the reliability (and reusability) of a model. To be able to determine whether a model is consistent, the model should be phrased in an unambiguous way, that is, in a notation with a clear and precise meaning. See slide 3-coherent. Also, to make the task of consistency checking manageable, a model should be as abstract as possible, by leaving out all irrelevant details. To establish the consistency of the combined model, covering structural, functional and dynamic aspects, the interaction between the various models must be clearly defined. Currently, to my knowledge, there is no completely developed method encompassing the structural, functional and dynamic aspects of a system in a manner that is amenable to a rigorous formal approach. However, there is an emerging understanding of how to deal with these various aspects. Moreover, there are attempts towards a standardization of the notions employed in the various methods. See sections OMG and methods.