Stream reasoning and complex event processing in ETALIS

Addressing the dynamics and notification in the Semantic Web realm has recently become an important area of research. Run time data is generated by multiple social networks, sensor networks, various on-line services, and so on. The challenge is how to get advantage of a huge amount of real time data, i.e., how to integrate heterogeneous data streams, combine data streams with the background knowledge (ontologies), and perform stream reasoning. In this paper we describe ETALIS system which enables specification and monitoring of changes in real time. Changes can be specified as complex event patterns, and ETALIS system can detect complex events in real time. Moreover the system can perform the task of reasoning over streaming events (e.g., RDF triples) with respect to the background knowledge (e.g., ontologies). ETALIS system implements two languages for event patterns: ETALIS Language for Events, and Event Processing SPARQL. The described system has various applicabilities in capturing changes in semantic networks, broadcasting the notifications to interested parties, and creating further changes (based on processing of the temporal, static, or slowly evolving knowledge).