The Semantic Web o?ers new options for information processes. Dr. Visser is dealing with twocore issuesin this area: the integrationofdata onthe sem- tic level and the problem of spatio-temporalrepresentation and reasoning. He tackles existing research problems within the ?eld of geographic information systems(GIS), thesolutionsofwhichareessentialfor animprovedfunction- ity of applicationsthat makeuse of the Semantic Web (e.g., for heterogeneous digitalmaps).Inaddition, theyareoffundamentalsigni?canceforinformation sciences as such. In an introductory overview of this ?eld of research, he motivates the - cessity for formal metadata for unstructured information in the World Wide Web. Without metadata, an e?cient search on a semantic level will turn out to be impossible, above all if it is not only applied to a terminological level but also to spatial-temporal knowledge. In this context, the task of infor- tionintegrationisdividedinto syntactic, structural, andsemanticintegration, the last class by far the most di?cult, above all with respect to contextual semantic heterogeneities. A current overview of the state of the art in the ?eld of information in- gration follows. Emphasis is put particularly on the representation of spatial and temporal aspects including the corresponding inference mechanisms, and also the special requirements on the Open GIS Consort