Subgraph error-correcting isomorphisms for syntactic pattern recognition

The structure-preserved error-correcting graph isomorphism proposed by Tsai and Fu (1979) for matching patterns represented by attributed relational graphs is extended to the case of subgraphs. The resulting subgraph error-correcting isomorphism, which includes the structure-preserved error-correcting graph isomorphism as a special case, is useful for recognizing partially viewed or structurally distorted patterns. After formulating a subgraph error-correcting isomorphism as a state-space tree-search problem, heuristic information useful for speeding up the search is suggested and an ordered-search algorithm is proposed for finding an optimal subgraph error-correcting isomorphism.