Research On Semantic Web Knowledge Reasoning Based On Description Logic

Description Logic is the object-based formal way to represent knowledge, it depends on the provided constructors and construct the complex concepts and roles on the simple concepts and roles. This article, on the basis of the basic description logic ALC, adds the constructors such as maxcardinality restriction(≤nR. C), mincardinality restriction(≥nR. C), transitive role(R+),inverse role(R-), union of roles(R₁∪R₂), composition of roles(R₁â—‹R₂), individuals set({a}) to extend the description logic, then we put forward the description logic ALC⁺. And we give the syntax and semantics of ALC⁺, and its formal axiom system, we also give some basic properties, which includes the idempotency law, the commutation law, the combination law etc. ;Then we analyse and proof the relation between the syntax inference and semantic inference. Checking the satisfiability of the concept that is represented by description logic is a key problem of the description logic reasoning problem, on the basis of the Tableau algorithm, which was put forward by Schmidt-Schauβ and Smolka, to check the satisfiability of ALC concepts, we give the way to check the general concepts that is represented by ALC⁺—Tableau-algorithm of ALC⁺, we also analyse and proof to get the conclusionthat other important reasoning problems (such as the concepts subsumption problem, the concepts equivalence problem, the concepts disjointness problem) can be reduced to checking the satisfiability of concepts. In addition, Semantic Web, which is put forward by Berners-Lee who is the beginner of WWW in 2001, mainly bases on XML and RDF/RDFS, it creates the ontology and the logical reasoning rules on this basis in order to accomplish the knowledge representation and reasoning on the basis of semantics. Then it is able to be understood and dealed with by computer. The research groups such as W3C put forward many advice and languages that aim at the representation of Semantic Web. These languages, which includes DAML (DARPA Agent Markup Language), OIL(Ontology Inference Layer),DAML+OIL, OWL(Web Ontology Language), constitutes the basis of Semantic Web. We give the corresponding relation between ALC⁺ and Web ontology languge OW, it is the syntax mapping, includes the constructor mapping and using ALC⁺ to describe the partial axioms of OWL. Nextly, we give an example that is using ALC⁺ to describe the knowledge that is represented by OWL and reason. Finally, we put forward the research aspects in the future.The description logic ALC⁺ which we put forward has a certain theoretical and practical value, it is suited for the application domain that the knowledge represented by the concepts classifying.