Searching Relation Paths Among RDF-Based Semantic Nodes

The Semantic Web is the combination of Artificial Intelligence and the Web technologies. The contents on Semantic Web are expressed by the eXtensible Markup Language (XML) and the Resource Description Framework (RDF). With XML, a user can define his own tags to identify data in a hierarchical structure, and place them in web pages to help computer programs to process the Web contents. RDF is a standard model for data interchange on the Web. It extends the linking structure of the Web and uses the Uniform Resource Identifiers (URIs) to describe the nodes and the relationships between the nodes on the Web in the form of a "triple". Using this simple model, it allows structured and semi-structured data to be shared across different applications.The most currently used RDF query language is SPARQL. Unfortunately, the current SPARQL standard only supports the basic pattern matching queries for RDF data, and dose not support searching the relation paths among RDF data nodes or around one node, which means it can not dig out the relationships among RDF nodes completely. So it is difficult to show the advantages of a RDF data model over the other models. In practical applications, doing basic pattern match queries is necessary; however, in many cases digging out the relations among RDF nodes is also important.After carefully analyzing the Semantic Web standards, a new extended SPARQL standard is proposed and implemented under Jena to support searching the relation paths among the RDF nodes. In order to achieve this objective, part of the SPARQL syntax in W3C standards is extended firstly by introducing some new keywords to the original syntax to express searching the relation paths among RDF nodes; then the structure of the ARQ engine is redesigned and the realization of the new SPARQL standards is added to the new structure. In the process of redesigning the ARQ engine, the directed graph model is used to replace the original iterator model to improve the query efficiency. Considering the data structure features of the relation paths among RDF nodes, a relatively efficient sorting algorithm is applied to sort the query results to ensure that the search results can really meet the real needs of users. With the extended SPARQL standards, the value of the RDF data model can be fully mined and utilized.