Constraints for validation of conceptual graphs

The works on validation propose solutions to ensure the quality of knowledge based systems. We are interested in the validation of a specific model of knowledge representation: the conceptual graph model. We present a semantic validation of conceptual graphs based on constraints given by an expert. The semantic validation of a knowledge base composed of conceptual graphs consists in checking its quality according to two kinds of constraints. The existential constraints allow one to express knowledge which must be deduced or which must absolutely not be deduced from the knowledge base. The descriptive constraints characterize the properties a conceptual graph must verify in the knowledge base. Descriptive constraints can be minimal or maximal to express the notions of "at least" and "at most". We introduce the notion of specification which is a combination of constraints linked by logical operators. The validation of a knowledge base is made according to these specifications, by means of a conceptual graph operation: the projection.