Enviromental data is frequently uncertain and incomplete.
Heterogeneous data structures as well as multimedia data have to be managed by the system. For interactive queries, the system should allow vague queries and query formulations that are independent of the specific structure of the data and its representation. For vague queries and imprecise data, methods developed in information retrieval can be applied. Heterogeneous data structures can be handled with concepts from object-oriented database management systems. Doc 157 Logic Programming and Databases - Ceri, Gottlob et al.