Abstract
Semantic Web refers to a Web of linked data in which data can be shared and reused, allowing more uses than the traditional 'Web of documents'. However, most of the information on the Web is stored in relational databases and such databases cannot be used by the Semantic Web. Relational databases can, however, be used to construct an ontology as the core of the Semantic Web. We propose a new approach which enables Semantic Web applications to access data actually stored in relational databases using a corresponding ontology. In our approach, domain ontologies can be used to formulate relational database queries in order to simplify the data access of the underlying data sources. The method we propose involves two main phases: the construction of a local ontology from a relational database and a semantic query in a relational database using relational database query language (RDQL). In the first phase, we construct a Web ontology language ontology from data in a relational database. In the second phase, we propose a technique to automatically extract the semantics of relational databases and transform this information into a representation that can be processed and understood by a machine. The method proposed is simulated and implemented using Jena and the simulation results show the effectiveness of the proposed approach. Therefore, we propose RDQL as a real alternative to the commonly used structured query language access to relational databases.
Highlights
The use of a structured query formulation language is one way to retrieve information in information management systems
We investigate the combination of OWL ontology and an exemplary semantic query language – relational database query language (RDQL) – in order to achieve an alternative for ordinary query using structured query language (SQL)
One of the major requirements of ontology-assisted query formulation systems and for performing semantic queries on a relational database is the formulation of a domain ontology which includes a definition of domain metadata, relationships and knowledge of the ontology
Summary
The use of a structured query formulation language is one way to retrieve information in information management systems. In contrast to menu driven or query by example (QBE) information access methods,[1] writing structured queries is a powerful method to access data because it allows endusers to formulate complex database queries. This method forces endusers to learn specialised query languages. Laborda and Conrad[2] introduced a representation format for both schema and data information based on Web ontology language (OWL) The advantage of their approach is obvious – relational data is able to be processed for Semantic Web applications using built-in functionality like query languages or reasoning mechanisms. The present analysis has been limited to whether the combination of OWL ontology and RDQL is capable of providing the same results as the relational algebra
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