What is Spatial Change

Integrating spatial and temporal dimensions is a fundamental yet challenging issue in modeling geospatial data. This article presents the design of a generic model within the object-oriented paradigm to represent spatially-varying, temporally-varying, and spatio-temporally-varying information using a mechanism, called parametric polymorphism. This mechanism allows a conventional data type (e.g., string and integer) to be enhanced into a spatial, temporal, and/or spatiotemporal collection type, and so an ordinary attribute can be extended with spatial and/or temporal dimensions flexibly. An associated object query language has also been provided to support the manipulation of spatio-temporal information. The design of the model as well as the query language has given rise to a uniform representation of spatial and temporal dimensions, thereby offering a new option for the development of a spatio-temporal GIS to facilitate urban/environmental change tracking and analysis.