A Research Of RDF Query And Storage

The key point of the Semantic Research is how to transform the information into the form that the computer can understand and process, which is semantic. Berners-Lee presented the hierarchy of the Semantic Web which is based on XML and RDF/RDFS. Ontology and logical inference rules is built upon them to represent the semantic knowledge and inference so as to be understandable and processed by the computer. The kernel of the Semantic Web is the ontology. Formalized ontology can not only describe the relevant concepts of the specific domain, but also depict the relations between the concepts. RDF supplies a simple but powerful data model to describe the resources. RDF model is defined as follows: contains a series of node; contains a series of property; the model is a set of triples; every data model can be seen as a entity-relation graph. RDF data model is actually a representation of duality and any complicated relation can be decomposed by many dualities. Therefore, RDF model can be the infrastructure of any complicated relation model.This paper emphasizes on the flexible query of the RDF data. On the one hand, utilize the class hierarchy in the ontology to expand the scope of user query; on the other hand, introduce the fuzzy set to represent the fuzzy data and user query and give the method of ordering the query results. Finally, the feasibility and the performance of the fuzzy flexible query model are verified in the merchandise fuzzy flexible query system, RDFLab.The content of the thesis can be described as following:First, the thesis reviews the development and background of the semantic web, containing XML, RDF, RDFS and OWL. Analyze the characteristic and storage of the RDF data and compare several RDF query language.Second, advance the theory and technology of the fuzzy flexible query. Build a vocabulary to make the domain of a fuzzy set and record the fuzzy set into the RDF data in the way of tagging; introduce keywords to improve the query efficiency; advance a fuzzy query language FRQL to facilitate the user query and hide the details of the system; show the method of ordering the query results; add the class of the query according to the ontology.Then, build a merchandise fuzzy flexible query system RDFLab, implement the FRQL in it and describe the system schema of the system and the functions and details of each module. Many performance tests are conducted to compare three kinds of close-degree and two storage patterns and improve the performance.With the swift development of the Semantic Web, more and more attention is paid on it and open source tools become abundant and perfect such as Jena2. However, the knowledge of the semantic web is still confined in small scope of some professional and institutes. There is no semantic and RDF tools for ordinary people like browser. RDFLab supply an efficient way of querying RDF data and is driven by domain ontology, so it has practical values.The main research contents of this thesis can be concluded as following:1) Advance a fuzzy flexible query theory by introducing the concepts of the fuzzy set into the flexible query to process the fuzzy network data and user query and give the method of ordering the query results.2) Advance a fuzzy flexible query FRQL to supply the users an efficient way of querying and implement fuzzy flexible query of RDF data.3) Apply the theory of fuzzy flexible query and FRQL, develop a merchandise fuzzy flexible query system RDFLab and improve the performance of the system.