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Graph transformation provides an intuitive mechanism for capturing model transformations. In the current paper, we investigate and compare various graph transformation tools using a compact practical model transformation case study carried out as part of the AGTIVE 2007 Tool Contest [22]. The aim of this case study is to generate formal CSP processes from high-level UML activity diagrams, which enables to carry out mathematical analysis of the system under design.

In this paper we show how isomorphism checking can be used as an effective technique for symmetry reduction in graph-based state spaces, despite the inherent complexity of the isomorphism problem. In particular, we show how one can use element-based graph certificate mappings to help in recognising nonisomorphic graphs. These are mappings that assign to all elements (edges and nodes) of a given graph a number that is invariant under isomorphism, in the sense that any isomorphism between graphs is sure to preserve this number. The individual element certificates of a graph give rise to a certificate for the entire graph, which can be used as a hash key for the graph; hence, this yields a heuristic to decide whether a graph has an isomorphic representative in a previously computed set of graphs. We report some experiments that show the viability of this method.