A Comparative Study on Representing RDF as Graph and Hypergraph Data Model

The semantic web gives a common framework that enables data to be shared and reused crosswise communities and applications. Semantic web depends on Resource Description Framework (RDF) graph data model, which is a standard model for data interchange on the web. Therefore, the success of the semantic web mainly relies upon the good creation of RDF. A powerful representation formalism for both structured and unstructured data are graphs that can be seen as a unified data representation. Also the development of the semantic web requires accessing large quantities of data stored in relational databases (RDB). Making data hosted in RDB machine understandable to the semantic web has been an active field of research during the last decade. Some of graph models that are used for representing an RDF succeed to solve some problems like blank nodes, reification, and answering queries posed by users and software agents, but fails in other problems like semantic reasoning and RDF query evaluation techniques. Also in the area of representing RDB as RDF graph data model none of these models defined a formal model for RDF graph model. Some database features like the normalization, function dependency, and query optimization does not address in the current graph representations. The purpose of this study is to present the important contributions that have been produced in the area of representing RDF as graph and hypergraph data model. Two models for representing relational database as an RDF graph data model are also reviewed.