(IJACSA) International Journal of Advanced Computer Science and Applications, Vol. 7, No. 11, 2016 7 | Page www.ijacsa.thesai.org OWLMap: Fully Automatic Mapping of Ontology into Relational Database Schema Humaira Afzal Department of Computer Science COMSATS Institute of Information Technology, Lahore, Pakistan Mahwish Waqas Department of Computer Science COMSATS Institute of Information Technology, Lahore, Pakistan Dr. Tabbassum Naz Department of Computer Science & IT University of Lahore, Lahore, Pakistan Abstract—Semantic web is becoming a controversial issue in current research era. There must be an automated approach to transform ontology constructs into relational database so that it can be queried efficiently. The previous research work based on transformation of RDF/OWL concepts into relational database contains flaws in complete transformation of ontology constructs into relational database. Some researchers claim that their technique of transformation is entirely automated, however their approach of mapping is incomplete and miss essential OWL constructs. This paper presents a tool called OWLMap that is fully automatic and provides lossless approach for transformation of ontology into relational database format. Number of experiments have been performed for ontology to relational database transformation. Experiments show that proposed approach is fully automatic, effective and quick. Our OWLMap is based on an approach that is lossless as well as it does not loose data, data types and structure. Keywords—Semantic Web; Ontology; Database; Mapping; OWL; Jena API I. INTRODUCTION The concept of semantic web is the extension of current web from human readable form to machine processable form by adding semantics. By applying structured information in semantic web, machines are capable to search, process, integrate and present the information in a meaningful and intelligent manner. Conventional search engines dissatisfy users by retrieving inadequate and inconsistent results because they work on predefined standards, terms that work in centralized environment. By semantic and ontology users are able to develop new facts and use their own keywords in different environment [1]. There are different techniques for storing ontology. Ontology can be stored in flat files [2]. But this technique does not provide scalability, query and other functionalities that database system can provide. Ontology repositories are used to hold ontology saved by Ontology management system [3]. But query facility in ontology management system is not as efficient as in relational database system. Relational database system has many advantages as compared to ontology management system like performance, robustness, maturity, reliability and availability. If ontology is stored in relational format then it can easily interoperate with large amount of existing web data. By using SQL, it is easy to retrieve information provided by ontology. If ontology is transformed into relational database then it will make semantic web more useful. Previous researchers have worked on mapping of RDF/OWL concepts into relational database. But these mapping approaches have certain problems like loss of structure, loss of data and perform only initial mappings i.e. tables to classes and columns to properties. Most of transformation tools are semi-automatic and need human intervention [4]. We attempt to explain these problems and provide a solution in the form of OWLMap. The structure of this paper is as follows. In Section 2, previous approaches and their drawbacks have been provided. Section 3, describes proposed methodology. In Section 4, explains the implementation of our approach with the help of case study. Section 5; describe the important phase of testing. Section 6, concludes the main points of paper and give some future directions. II. RELATED WORK Reference [5] has purposed an approach for transformation of OWL to ER and vice versa by using conceptual graphs. The transformation is performed step by step, where the first phase is to transform the OWL ontology to ER and second phase is to transform ER to relational database. Reference [6] used “Oracle Semantic data storage” approach for transformation, but most OWL constructs are missing in this approach. Reference [7] suggested the “Storing ontology includes fuzzy data types” approach. Reference [8] purposed “large scale ontology management” approach that covers some constructs of OWL and transformation tool is not fully automatic. Rule based transformation presented by [9] and [10] are based on “mapping rules”. The short comes of these approach is that few constructs are missed during transformation. Few sub-properties and few constructs of OWL ontology are not considered e.g. property restrictions. OWL2DB algorithm is another approach to map OWL documents into relational tables without any human intervention [11]. The transformation is incomplete and it only saves class instances in relational format. Reference [12] proposed an approach for mapping of ontology to relational database. This approach is tested on ontology selected from product configuration domain. This approach covers only a few part of OWL DL syntax. In “Mapping of OWL ontology concepts to RDB Schemas” approach purposed by [13], authors purposed some mapping principles and algorithm. The prototype tool has been added as plug-in for an ontology editor named protégé.