Summary form only given. Today's distributed information systems often are collections of existing information sources and as such heterogeneous. Technical integration of heterogeneous sources is supported by CORBA. However, CORBA provides very general support and does not take source specific semantics into account. This also applies to CORBA's Event Service. Our objective is to enhance CORBA by mechanisms that allow to add application semantics. Our key idea is to provide a flexible configurable event monitoring service, which accepts heterogeneity, for a CORBA environment. Configurable means that we are able to generate code templates at compile time and to provide dynamic parametrization of parts of the service. Event passing semantics follow those developed for active database Event-Condition-Action (ECA) rules.

Many application areas require the integration of heterogeneous information sources into a coherent distributed information system. With such systems, users frequently need not only be able to access information, but they also have to be notified automatically when new information that is relevant to their work becomes available. For example, an our environmental systems project, a civil servant needs to be informed when a measured air quality parameter exceeds a certain threshhold. Detection of such a critical situation requires subsequent monitoring of several data sources (e.g., a database recording measurement values and a database with limit values). The paper presents an approach for such situation monitoring which is based on CORBA, for the technical integration of heterogeneous systems and on active DBMS-style ECA-rules. In particular, it discusses how ECA-rules can be adopted in a CORBA environment, and describes a CORBA-based system for situation monitoring. The major implementation issues addressed are event detection within autonomous component systems and detection of complex distributed situations.