We introduce a specification language, Promela-Lite, which captures the essential features of Promela but which, unlike Promela, has a formally defined semantics. We show how we can detect symmetry in specifications defined in Promela-lite by constructing a directed, coloured bipartite digraph called a static channel diagram, and applying computational group theoretic techniques. We extend our approach to Promela and introduce a tool, SymmExtractor, for automatically detecting symmetries of

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... ela specifications. We demonstrate the effectiveness of our approach via experimental results for a suite of Promela specifications. Unlike previous approaches our technique is fully automatic, and not restricted to fully symmetric systems.