Simple conceptual graphs are considered as the kernel of most knowledge representation formalisms built upon $owa's model. Reasoning in this model can be expressed by a graph homomorphism called projection, whose semantics is usually given in terms of positive, conjunctive, existential FOL. We present here a family of extensions of this model, based on rules and constraints, keeping graph homomorphism as the basic operation. We focus on the formal definitions of the different models obtained, including their operational semantics and relationships with FOL, and we analyze the decidability and complexity of the associated problems (consistency and deduction). As soon as rules are involved in reasonings, these problems are not decidable, but we exhibit a condition under which they fall in the polynomial hierarchy. These results extend and complete the ones already published by the authors. Moreover we systematically study the complexity of some particular cases obtained by restricting the form of constraints and/or rules.

Abstract. Griwes is an initiative to develop a common model and an opensource freeware platform shared by different graph-based frameworks. We provide an overview of its objectives, architecture and specifications. We detail some of the basic mathematical structures that are used to characterize the primitives for graph-based knowledge representation. We then propose to factorize recurrent knowledge representation primitives that can be shared across specific graph-based languages and we provide a proof of concept by showing how two languages (Simple Conceptual Graphs and RDF) can be described in this framework.

Abstract. In this paper, we aim at showing the advantages of Conceptual Graph formalism for the Semantic Web through several real-world applications in the framework of Corporate Semantic Webs. We describe the RDF(S)-dedicated semantic search engine, CORESE, based on a correspondence between RDF(S) and Conceptual Graphs, and we illustrate the interest of Conceptual Graphs through the analysis of several real-world applications based on CORESE. 1

This article deals with the operational use of a domain ontology integrated into a Knowledge-Based System (KBS). It presents TooCoM, a tool dedicated to (1) the definition of ontologies with the Entity-Relationship paradigm and (2) the operationalization of ontologies in the context of the Conceptual Graphs model. TooCoM provides functionalities for specifying an operational scenario of use of the ontology which is under construction, for transcribing this ontology into the corresponding operational form and for using this operational form in an embedded inference engine.