May 21, 2009

Notes on CEP application development

While performance may not be all that great a source of CEP competitive differentiation, event processing vendors find plenty of other bases for technological competition, including application development, analytics, packaged applications, and data integration. In particular:

So far as I can tell, the areas of applications and analytics are fairly uncontroversial. Different CEP vendors have implemented different kinds of things, no doubt focusing on those they thought they would find easiest to build and then sell. But these seem to be choices in business execution, not in core technical philosophy.

In CEP application development, however, real philosophical differences do seem to arise. There are at least three different CEP application development paradigms:

Even more fundamental, however, is the question of event-driven programming. That’s a term which first was popular in the 1990s, signifying programs that — rather than being wholly procedural — listened for and responded to events, often in user interfaces. More generally, event-driven programming is inherent in almost any kind of loosely-coupled architecture, be it client-server, service-oriented, or whatever. But to hear some CEP proponents tell it, all that isn’t event-driven enough.

In particular, StreamBase recommended to me Gregor Hohpe’s paper Programming Without a Call Stack – Event-driven Architectures, which argues that if there’s any concept of procedure or method invocation at all, the whole thing is too “command-and-control” (Boo!!) and insufficiently event-driven to be well-suited for CEP. Rather, everything should be done on a fine-grained publish-subscribe basis. It’s an interesting argument. Usually, the problem with extremist programming paradigms is that the thing you write has to interface with the rest of the world, and by the time it accommodates itself to them, the paradigm is violated anyway. But if the essence of the paradigm is loose coupling to begin with, maybe that pitfall can for once be avoided.

Comments

5 Responses to “Notes on CEP application development”

  1. Charles Young on May 21st, 2009 4:55 am

    The use of Rete engines for complex event processing is a contraversial topic. Tibco’s engine is built on Rete. SAP Research has published a couple of papers on the subject in the last year or two, and the topic has been rattling around the academic community for several years now. My own view is that Rete engines are a useful tool in the CEP developer’s armoury, but are better suited to the upper reaches of an event processing network, close to the analytics and automated business processes, rather than close to ‘raw’ event observation.

    Microsoft’s use of their monadic LINQ technology makes huge sense on the MS platform where LINQ has already found very broad acceptance and is well-supported by ‘syntactic sugar’ in C#, F# and VB.NET. There may be support for managed C++ as well. LINQ allows MS to support CEP development in a natural fashion directly within mainstream GPLs rather than having to provide specialised DSLs and without having to modify those GPLs in any way.

  2. Ujin on May 21st, 2009 6:00 am

    Thanks for good article! I think that most of products, I mean tools for speeding up programming, have no tools for visual constructing a model of application.

  3. Paul Vincent on May 22nd, 2009 12:11 pm

    Actually, you can argue that CEP tools exploit all 3 of “data manipulation” (a.k.a. continuous query) languages, visual event-oriented programming, and rules (whether Rete-based, inferencing, or whatever).

    As Charles said, TIBCO’s BusinessEvents CEP tool utilizes Rete for rules (Rete = a pattern matching algorithm, hence its applicability to general CEP should be obvious regardless of its usage in “conventional” rule engines). But TIBCO also does the continuous query thing, and uses drag n drop state models as a type of “visual event oriented programming”. Other vendors’ ESP and CEP tools also provide combinations of these 3 mechanisms (although possibly not yet Rete, unless you add Drools 5 to the mix).

    The main philosophical aspect with “CEP” programming is the desire to process events as they occur, for whatever event patterns they impact. Truly “event driven” rather than “store and process in silos”…

    Cheers

  4. Curt Monash on May 22nd, 2009 12:31 pm

    Paul,

    I’ll admit to knowing much less about TIBCO’s CEP than other CEO offering. That’s because nobody at the company seems too concerned about changing this state of affairs. ;)

    CAM

  5. Marco Seiriö on May 27th, 2009 5:40 am

    I see that only 10%-20% of leads that I talk to have performance requirements that we in the CEP world would think of as “high performance”. Most of these problems can also be split on multiple independent servers, leaving only a few % which actually need monster performance on a single server or a cluster of servers.

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