ABSTRACT. We study anti-unification for possibly cyclic, unranked term-graphs and develop an algorithm, which computes a minimal complete set of least general generalizations for them. For bisimilar graphs the algorithm computes the join in the lattice generated by a functional bisimulation. Besides, we consider the case when the graph edges are not ordered (modeled by commutativity).

These results generalize anti-unification for ranked and unranked terms to the corresponding term-graphs, and solve also anti-unification problems for rational terms and dags. Our results open a way to widen anti-unification based code clone detection techniques from a tree representation to a graph representation of the code.