The Tripod spatio-historical data model

The storage and analysis of large amounts of time-varying spatial and aspatial data is becoming an important feature of many application domains. This has fuelled the need for spatio-temporal extensions to data models and their associated querying facilities. To date, much of this work has focused on the relational data model, with object data models receiving far less consideration. Where descriptions of such object models do exist, these models fail to fully integrate their spatial, aspatial and temporal dimensions into a uniform and coherent model. In addition, there is currently a lack of systems which build upon these models to produce database architectures that address the broad spectrum of issues related to the delivery of a fully functional spatio-temporal DBMS. This paper presents a foundation for the development of such a system, called Tripod, by describing a spatio-historical object model based on a specialized mechanism, called a history, for maintaining knowledge about entities that change over time. Key features of the resulting model include: (i) consistent representations of primitive spatial and timestamp types; (ii) a component-based design in which spatial, timestamp and historical extensions are formalized incrementally, for subsequent use together or separately; (iii) compatibility with mainstream query processing frameworks for object databases; and (iv) the integration of the spatio-temporal proposal with the ODMG object database standard. The paper presents a comprehensive formal characterization of the model and illustrates its capabilities in a crime data management application. It is also shown how the model can be programmed using an extension to the ODMG language bindings. The model and language bindings have been fully implemented. 2003 Published by Elsevier B.V.