Various Events Involved in Spatio-temporal Databases

In general, time has two kinds of semantic, i.e., time-scale semantic and event-sequence semantic (Shu Hong, 1998). In spatio-temporal databases (STDB), time-scale semantic refers to the time positioning of geographical objects, and event-sequence semantic to spatial and thematic change description. Here event and change are alternatively termed without further meaning distinction. Almost a decade’s STDB research has been conducted, but few results have been brought into practice (Timos Sellis, 1999). This somewhat indicates that a gap exists between our theoretical research and users’ application requirements. In bridging this gap, spatio-temporal semantic modeling plays an important role, not only because semantics are derived from our understanding of practical problems, but also because they make sense our theoretical research. The objective of this paper is to explore primary events involved in spatio-temporal databases for various spatio-temporal phenomena modeling quantitatively or qualitatively. The paper is constrained to exploration of spatial events for the time being. Spatial changes are identified at three levels (scene change, object change and property change). At the level of property change, a set of primary spatial property changes (location change, distance change, direction change, size change, shape change), together with geometrical dimensionality changes (point change, line change, area change), are proposed. At the level of object change, in terms of mapping relationships between source objects and result objects, six kinds of object change are given. At the level of scene change, several primary scene changes and distribution type change are addressed. Various advanced spatial changes will surely enrich spatiotemporal semantic modeling in spatio-temporal databases.