Locally unique labeling of model elements for state-based model differences

Model versioning occupies a central position in model configuration management systems, which are considered integral ingredients in every large model driven engineering project. There are two major approaches in describing versions of models: the state-based approach and the change (operation) based approach. In both cases, the differences between two different versions of a model are called model differences. We focus on the state-based approach to versioning and show that in this case the model differences require a locally unique labeling for all model elements. Next, we specify a generic method for assigning unique labels to all model elements in versioned models. We also show that the described labeling method is also applicable to ambiguous models, i.e. models which contain structurally identical elements having the same parent element. The main application area of the presented method is the process of calculating model differences in case that modeling tools do not assign unique identifiers to all model elements.