vincent
Thu, 03 Jul 2008 16:59:44 +0000
Occasionally it is good to attend an academic [*1] conference in one’s field, and the Distributed Event Based Systems conference is considered one of the main events for CEP (although it includes a major dose of pub-sub / middleware topics too). Held in Rome, Italy, the conference organizers had a few challenges (such as flakey WiFi, and a lack of air con in the first venue that made for the novel experience of seemingly having conference sessions in a sauna) but the fascinating location (near the Colloseum) made up for any minor inconveniences.
Sharma Chakravarthy from the University of Texas kicked the tutorials day off by covering the Snoop representation for event operations. This seemed a neat way of modeling (some) aspects of event processing, including the fact that a composite event can represent multiple events which define a duration, making temporal operations tuple-based (i.e. with a start and end timestamp). This leads to a specific event-notation (with maybe some similarities to ORM), and “interval-based semantics” for composite event operators (which look like they might be overly complex for typical use cases and CEP users). Snoop seems to have been around for years (see this 1993 reference!). I have to say that the references to Active Databases made for a good history lesson, but also made the tutorial seem outdated (e.g. as an exercise, consider how you might relate the terms “active database” and “distributed event”).
The Snoop info was interesting (for anyone who hasn’t seen it before), but I was hoping for more on patterns and uses for combining ESP with CEP, per the tutorial title (”Events and streams, harnessing and unleashing their synergy”). Indeed the session started with the basic concept of processing streams before combining their resulting high level events - certainly a CEP design pattern which is of particular interest to TIBCO BusinessEvents users.
Cruel relief was provided during Sharma’s “EP operations are not database operations” comments [*2], which for some reason seemed to annoy the heck out of the Oracle guys…
Notes
[1] DEBS included a number of industry presentations, but many of these represented “R&D” updates from vendors. For a more commercial conference, but with less technical detail, consider the Gartner event later in the year. Many CEP and EP vendors were present (NetZero, Streambase, Oracle-the-database-storing-events, Oracle-the-Weblogic-app-server-version-for-events, WareLite), as well as vendors from other technologies such as BRMS/BRE (ILOG), ERP (SAP), RDF-store (Franz), etc.
PS: googling for DEBS2008 or DEBS08 will likely hit a number of, er, unrelated and possibly work-unfriendly sites. Use the search term DEBS 2008 CEP for a better success rate.
[2] Sharmy had an excellent comparison slide on “DBMS” vs “data stream management systems”. This went through their respective attributes, which looked approximately like:

1. persistent relations vs transient streams
2. ad hoc vs continuous queries
3. random vs sequential access
4. unbounded disk store vs bounded memory store
5. only current state vs history / arrival order critical
6. low update rate vs high data rate
7. no real-time services vs “real-time” requirements
8. precise results vs approx results
9. transaction mgmt vs no transaction mgmt (e.g. rollback)

To show how current CEP tools might fare in this comparison, lets see which attribute best applies to TIBCO BusinessEvents: 1. both, 2. both, 3. both, 4. both, 5. both, 6. high data rate, 7. “real-time”, 8. precise results, 9. no “transaction management”. Not bad (and you could argue that transactions are just managed “differently” in an EDA).


Source...