AN OBJECT ORIENTED SPATIO TEMPORAL DATA MODEL IN GIS
Gong Jianya (Wuhan Technical University of Surveying and Mapping, Wuhan, 430070)
It is difficult for current Geographic Information System(GIS) software to deal with temporal phenomenon, so 3 D and 4 D temporal data models have now been becoming an issue that is receiving attention in the GIS area. Many scholars have advanced a lots of temporal data models. After proposing the object oriented data model(OODM) based on an integrated vastervector data structure, the author of this paper further discusses the temporal phenomenon in the real world, and introduces time dimension(time D) to OODM. There are three approaches to representing the historical changes of spatial objects in a database: stamping version information on a relational tables, on records, and on attributes. The paper introduces an object oriented approach to stamping a version information on attributes, so that attribute values of an object in different periods can be described directly. It not only saves the storage space, but also is more convenient to retrieve an spatial object and quarry over a historical event. This data model represents the 3 D spatial and temporal information, and their relations including attribute data, geometric data(vector and raster), topological relations and time. It can be established using a unified model. Finally, an new approach to record version using object identification(OID) and path to realize the spatio temporal data model are proposed.