The Use of Ontologies in Location-based Services: The Space and Time Ontology in Protégé

Abstract. As location-based applications become part of our everyday life, ranging from traffic prediction systems to services over mobile phones providing us with information about our surroundings, the call for more semantics and accurate services related to them is emerging. Moreover, the need for integration of multiple data sources calls for an abstract location model, easily understandable to domain experts. In this paper, we study and analyze the concepts involved in Location-Based Services (LBS); three of them, namely space, time and movement are fundamental and have common characteristics in all LBS applications. We first present a systematic analysis and structure of space, time and movement, register their characteristics and their relations. In order to (a) make LBS assumptions that already exist in literature about space, time and movement explicit (b) share common understanding of their structure, and (c) enable reuse of this LBS knowledge, we use long-praised technique of ontologies to organize and design them. More specifically, we introduce an ontology structure for LBSs consisting of the Domain Ontology, the Content Ontology and the Application Ontology. The proposed design of space, time and movement constitute the Domain Ontology. We design the Domain Ontology of LBS in Protégé, an open-source, extensible-code tool, allowing for the easy and understandable representation of ontologies from experts. The presented Domain Ontology is component of the knowledge base of a fleet management system handling traffic in the Athens Metropolitan Area