Ontology Enabled Graphical Database Query Tool for End-Users

Abstract. In this paper we show how semantic web technologies are used in a real application in the domain of national medical databases where an important technological gap between the legacy relation databases and OWL ontologies is bridged by the recently standardized UML profile for OWL. After data has been exported from multiple relational databases into a single shared RDF database structured according to an integrated OWL ontology there emerges a need for a convenient end-user query tools. We describe a fully graphical access to the exported data through the graphical front-end tool (named “DEMO” tool) based on the UML profile for OWL and SPARQL query language. Keywords . semantic web, ontologies, information system design, database design, RDF data stores, modeling languages, data semantics Introduction Semantic web technologies such as RDF and OWL are lately starting to find promising and somewhat unexpected applications also in the field of information system engineering which traditionally has been based on the SQL driven relational databases [1, 2]. Despite relative inefficiency of RDF databases and SPARQL [3] query language (compared to the more mature relational databases) the flexibility of RDF to directly integrate data with its conceptual model (OWL domain ontology) removes a historic barrier from the databases – the end-users now can query data from the database themselves by knowing the OWL ontology only, rather than rely on the “man in the middle” (a programmer, who creates the application-specific user interface for the database) to reformulate the end-user queries into the SQL statements over the hidden, implementation-specific normalized relational database schema. The problem is that in the legacy relational databases the initial conceptual model of the domain (often modeled as UML class diagram or ER-diagram) tends to disappear during conversion into the normalized database schema thus leading to database being inaccessible for direct query by domain experts familiar only with the conceptual model. Additional benefit added by RDF and OWL is the hierarchical scalable URI namespace, which eases the integration of previously separate databases. Such integration is aided also by the rich and yet strictly formal semantics of OWL DL. The richness of OWL DL provides means for modular abstraction levels over narrower domain ontologies during the database integration such as