In the past few years the classical distinction in GIS between geometry - handled by specialized GIS modules - and attributes - treated in small integrated databases or exported to large external databases - has started to fade out. Several vendors of database products recently introduced spatial extensions for their systems, as for example the Spatial Data Option (SDO) from Oracle, the Spatial Datablade for Informix or the spatial data support in OpenIngres. They are mostly extensions to support spatial data types such as points, lines and polygons, but compared to geographic information systems, they provide little support for spatial analysis. A different approach was taken by ESRI, the producer of Arc/Info, by developing a spatial platform on top of large commercial database systems, called Spatial Database Engine (SDE), which allows to store both geometry and attributes in the database in a transparent way. Nevertheless both DBMS and GIS vendors focus on the 'snapshot oriented' systems concerning temporal aspects.