Fuzzy data modeling and algebraic operations in RDF

The Resource Description Framework (RDF), a language proposed by the World Wide Web Consortium (W3C), is a flexible model for representing information about resources on the Web and has been applied in many application areas. At the same time, information is often imprecise and uncertain in many real-world applications. The existing works of RDF fall short in the ability of modeling imprecise and uncertain data in RDF. In this paper, we introduce some basic notions of fuzzy RDF graph model based on fuzzy sets. Along with the fuzzy RDF model, a fuzzy RDF algebra is formally proposed and a set of algebraic operations are developed. We also present some algebraic equivalences based on data graph isomorphism which can be used to rewrite algebra expressions in a form that satisfies certain needs. Finally, we show how to apply the proposed algebraic operations to capture the queries expressed in SPARQL query language. Based on the proposed data model and algebraic operations, we discuss the implementation issues.