Abstract

We present a shape de nition language, called SDL, for retrieving objects based on shapes contained in the histories associated with these objects. It is a small, yet powerful, language that allows a rich variety of queries about the shapes found in historical time sequences. An interesting feature of SDL is its ability to perform blurry matching. A "blurry" match is one where the user cares about the overall shape but does not care about specific details. Another important feature of SDL is its efficient implementability. The SDL operators are designed to be greedy to reduce non-determinism, which in turn substantially reduces the amount of back-tracking in the implementation. We give transformation rules for rewriting an SDL expression into a more efficient form as well as an index structure for speeding up the execution of SDL queries.

Citations