Semantic CEP

From RDF Stream Processing Community Group

This wiki page reports on the activities around the Semantic Complex Event Processing (SCEP) within RSP. We want to leverage RSP-QL to support some level of SCEP by identifying what is missing and characterizing short- and long- term goals.

Key Ideas

  • Use RSP to reduce the input at CEP level
  • Enable State Management to define operators for summarization/aggregation
  • Ability to feed back results into the stream (loop-back new stream?)
  • Would that scale? Implementation can be different than RSP-QL language specification
  • Application dependent aspects (long-term)
    • Mathematical operators
    • Geospatial calculation


  • time interval
  • tumbling windows in CEP

Managing Graphs

  • Need to uniquely identify a graph to refer to it later
  • Same named graph (one event) could have unique identifier but different timestamps

State Management

  • Access to timestamps (e.g. for partial computation of substreams)
  • Store state of previous event

Stateful operators

  • SEQ (need optional binding), REP
  • Clean Closure (e.g. same event with different temporal values)
  • Selection strategies (e.g. skip till next)
  • Correlations of results of sub-patterns into one query
  • More longer-term: property paths, nested construct queries, negation, ...

Use Cases in SCEP

Implementation Issues

This is a longer-term aspect of SCEP activities within RSP. The key point to keep in mind for now is that the implementation can happen by extending specific engines or as part of a new engine implementing RSP-QL with embedded SCEP.