Conceptual Graphs Isomorphism: Algorithm and Use

The isomorphism problem is neither known to be NP-complete nor polynomial. Yet it is crucial for managing large conceptual graph sets. In order to speed up the conceptual graph isomorphism test, we associate to graphs a textual code that is invariant under isomorphism: a structural or ltering code. The structural code of a given graph is based on the computation by a structural function of an intrinsic total preorder on its conceptual vertices. Moreover for graphs for which the structural function produces a total order on conceptual vertices, two graphs which have the same code are isomorphic. Then, we present a conceptual graph set managing system based on the specialization relation and on a hashing function on the code induced by a structural C-preordering function. This system allows an eeective search for a given conceptual graph according to its structure and so determines its specialization / generalization graphs without any projection test.