Abstract
Space and time have not received much attention on the Semantic Web so far. While their importance has been recognized recently, existing work reduces them to simple latitude-longitude pairs and time stamps. In contrast, we argue that space and time are fundamental ordering relations for knowledge organization, representation, and reasoning. While most research on Semantic Web reasoning has focused on thematic aspects, this paper argues for a unified view combining a spatial, temporal, and thematic component. Besides their impact on the representation of and reasoning about individuals and classes, we outline the role of space and time for ontology modularization, evolution, and the handling of vague and contradictory knowledge. Instead of proposing yet another specific methodology, the presented work illustrates the relevance of space and time using various examples from the geo-sciences.