Active change notification in advanced knowledge base servers

"Intelligent" behavior of database systems is often seen restricted to comfortable support for query answering (including limited forms of reasoning) and navigating within the stored data. However, active notification for clients about changes in the database is an important requirement for advanced interaction between the database and its client applications. These usually hold (derived) subsets of the database contents under their control. The incremental maintenance of such externally materialized views is an important open problem. In addition to some necessary changes in the known view maintenance procedures the issue of translating updates through an API and a way for clients to accept such updates have to be defined. We describe the main features of a solution to this problem implemented in the knowledge base server ConceptBase.