A Recursive Continuous Query Language for Integration of Streams and Graphs

Abstract

Query processing data streams obtained from sensors becomes more and more important today. We have many kind of query processing requirements for not only a single stream, but also multiple streams from different sensors. To utilize multiple streams, we have to consider positional relationships between sensors. Conventionally, they are represented by distances in the 3-dimensional space, or a hierarchy of logical areas (e.g. rooms/floors/buildings). Some stream applications need more sophisticated relationships that are represented in a graph structure. However, query languages for streams are not integrated with ones for graphs, thus we cannot uniformly treat them in the same language. This paper proposes a DataLog-like query language which can utilize multiple streams from streams having graph relationships. The proposed query language supports continuous queries on streams by containing event specifications and sliding-windows for streams. And, it also supports recursive search for graph relationships.