The role of a multi-tier ontological framework in reasoning to discover meaningful patterns of sustainable mobility

The successful applications of Geographical Knowledge Discovery in Databases (GKDD) are not common, despite the vast literature on knowledge discovery in databases. Although it is relatively straightforward to find patterns in very large spatio-temporal databases, establishing their relevance and explaining their causes are both very complex problems. In practice, spatio- temporal databases are not adequate to handle geographical knowledge in an ad-hoc manner, and as a result, most of the patterns found in a GKDD process may well already be background knowledge, which refers to the common sense reasoning of a geographical knowledge domain. Addressing these issues requires considering a geographical knowledge discovery process as a multi- tier ontological process, in the sense that more complex reasoning modes can be used to help the comprehension of what makes one pattern structurally and meaningfully different from another. Towards this goal, this Chapter proposes a multi-tier ontological framework to support a GKDD process. Three ontological tiers are described to provide the common base for the organisation of different nature and sources of knowledge as well as the reasoning tasks integrated within a spatio-temporal database. They are: Domain, Application and Data Ontology Tiers. The potential of this approach is illustrated on (a) reducing the semantic gap between an ontological tier and a database representation by using mappings between the ontology and conceptual model, and (b) permitting to define spatio-temporal relationships within an ontology, which can be translated to spatio-temporal conceptual queries. The implementation has been carried out as a proof-of-concept and the specific information metaphor of movement-as-trajectory has been used to illustrate the implementation of the Data Ontology Tier. The preliminary results are pointing out that geographical knowledge of sustainable mobility must come from a global and systemic view of patterns within a GKDD process, and the important role of a multi-tier ontological framework on the integration of semantic abstractions (concepts), reasoning tasks, and patterns. They had also drawn attention to the fact that combining ontological representation with database querying mechanisms is fundamental for the use information metaphors in GKDD processes.