MODELLING, QUERYING AND DEVELOPING SPATIOTEMPORAL APPLICATIONS BASED ON VRML
Alex Vakaloudis, Babis Theodoulidis
Timelab, Dept. of Computation
Despite the number of proposals for processing 2D spatial data, the areas of 3D spatial information is still quite empty. Moreover, only few attempts appear towards incorporating the temporal and the 3D spatial domains. At the same time the vast growth of Internet and WWW has set a new domain for applications. One of the most promising Web browser plug-ins is VRML, the means for 3D spatial navigation. With the work presented in this paper we wish to extend this functionality by providing temporal navigation, data storage and spatiotemporal querying. The result is an architecture for 3D Spatiotemporal databases accessible over the Internet. A data model for spatiotemporal applications (3D-STDM) is analysed. It follows a technique separating spatial and non-spatial information. A bridge table is used to connect these two parts. The spatial part is described by a set of tables that cover the spatial and the positional characteristics of an object. By timestamping the object tuples and identifier, a unified spatiotemporal entity is generated. It has continuous temporal characteristics; two successive object states are connected via the trend field which records the object transitional evolution. A query language (3D-STQL) for spatiotemporal object manipulation is also provided. Apart from the operators, it contains predicates dependent or independent on userís viewpoint. It also includes temporal and spatiotemporal operators that capture specific spatiotemporal features. 3D-STQL is interfaced to VRML via WWW Browser providing remote access to spatiotemporal information. The entire framework complies with the VRML standard.
Keywords: VRML, Spatiotemporal Databases, Internet databases