Among other things I have done in DEBS 2011, I have also delivered one talk to present the paper on patterns rewriting, the paper, like all DEBS 2011 papers can be obtained from the ACM Digital Library.
The paper is co-authored by Ella Rabinovich (the primary author), Avi Gal and myself.
The presentation starts by classifying optimization tools in use for optimizing the performance of event processing applications, the classification is into blackbox optimization where the actual implementation is taken as a blackbox, and whitebox optimization, The paper deals with one of the types of whitebox optimization - pattern rewriting, which mean rewrite a pattern into a collection of other patterns that yield equivalent results: same output to the same input.
While rewriting exist in different areas such as rules or SQL queries, there is some inherent complexity in some of the event processing patterns such as SEQUENCE. The difficulty stems from the temporal relationship imposed by sequence, which imposes restriction on assertion splitting, and from the fact that policies may not be transferred in the rewriting process nicely. This was an exploratory research to see whether rewriting is a useful method for optimization, especially where complex sequences are involved. The experimental results in simulation for sequence with 16 operands (a real application we have done in the past in the web commerce area), shows that rewriting alone can improve the latency by more than tenfold and also the throughput, and no matter how the latency/throughput trade-off is weighted, some rewriting will give better result than no rewriting in this case.
The presentation can be viewed on slideshare. Enjoy!