The index organizations for RDF and RDF schema

In semantic Web, metadata and ontology for representing semantics and conceptual relationships of information resources are essential factors. RDF and RDF schema are the W3C standard models for describing metadata and ontology. Therefore, storing and querying RDF and RDF schema is one of major tasks in applications on the semantic Web. Many existing studies are mainly tailored to RDF triple statements without considering RDF schema. And most studies are focused on querying over simple triple statements and pass over various query forms such as keyword-based query and path-based query. In this paper, we propose two indexing techniques considering both RDF and RDF schema. First, we present a path index for processing structure-based query of RDF and RDF schema. Path index stores all path information in graph models of RDF and RDF schema and supports hierarchical relationships between classes or properties. Second, we describe a keyword index for processing keyword-based query. Keyword index stores all resources that contain indirectly or directly a certain keyword in RDF. So, if user's keyword is given, all resources that contain a corresponding keyword can be retrieved easily