Computer Systems Laboratory Colloquium

4:15PM, Wednesday, November 6, 2002
NEC Auditorium, Gates Computer Science Building B03
http://ee380.stanford.edu

Extending Publish-Subscribe with Relational Subscriptions

Rob Strom
IBM Research
About the talk:

Traditional publish-subscribe systems simply deliver to subscribers all messages published on a particular topic or all messages meeting a particular filtering criterion. If messages are lost, or if the subscriber is intermittently connected, a more reliable "guaranteed delivery" quality of service guarantees the eventual ordered delivery of all messages.

An alternative paradigm is to view a subscription as a request for a particular state derived from the published messages -- i.e. a continuous query. What is delivered to the subscriber is not necessarily the published message stream, but the updates to the state he is interested in. Now if messages are lost, then after recovery, the system can deliver the new state rather than a possibly large number of messages. This paradigm also allows subscribers to subscribe to derived events that are a function of summaries of message histories.

We discuss an exploratory effort in IBM's Gryphon publish-subscribe system to extend our reliable messaging protocols to support "relational subscriptions". We introduce a Relational Subscription Language (RSL), adapted from relational algebra, but based upon monotonic base relations and a monotonic type system. We discuss how monotonic type analysis allows an efficient "mostly push-based" implementation that combines timely delivery with scalability and fault-tolerance.

About the speaker:

Rob Strom has been a Research Staff Member at the IBM TJ Watson Research Center since 1977. His main research interests have been in programming languages, distributed systems, and optimistic algorithms. He is known for the design of Hermes, one of the earliest languages to simultaneously support type-safe multi-threaded multi-component applications, and of Optimistic Recovery, an efficient technique for transparent recovery of applications in a distributed environment. Rob's latest research interest has been in highly scalable distributed publish-subscribe systems. His latest research concerns applying techniques from incremental continuous queries of relational databases to the implementation of fault-tolerant messaging systems.

Contact information:

Rob Strom
IBM Research
Rob Strom