“…Formal modeling techniques provide the basis to validate the system design [39,40], to generate system level test suites [38,41,40,37,14,31,32], to simulate the system behavior by executing the model [42,18] and to determine properties of the system. Although modeling techniques can help eliminate complexity of many of today's systems, the resulting models are difficult to understand, analyze, and modify [28,29], especially for large and complex systems [27,47] where there are a large number of states and transitions. During software maintenance developers are frequently interested in a partial system model related to an element of interest, e.g., a requirement, a transition, or a feature [28,30,31,32,33,34], that they need to analyze, understand, or modify, e.g., slices of models [34,35].…”