Master's thesis in Computer scienceSemantic Web aims to elevate simple data in WWW to semantic layer, so that knowledge, processed by machine, can be shared more easily. Ontology is one of the key technologies to realize Semantic Web. Semantic reasoning is an important step in Semantic technology. For Ontology developers, semantic reasoning finds out collisions in Ontology definition, and optimizes it; for Ontology users, semantic reasoning retrieves implicit knowledge from known knowledge.
The main research of this thesis is reasoning of semantic data querying in distributed environment, which tries to get correct results of semantic data querying, given Ontology definition and data. This research studied two methods: data materialization and query rewriting. Using Amazon cloud computing service and LUBM, we compared these two methods, and have concluded that when size of data to be queried scales up, query rewriting is more feasible than data materialization. Also, based on the conclusion, we developed an application, which manages and queries semantic data in a distributed environment. This application can be used as a prototype of similar applications, and a tool for other Semantic Web researches as well
