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Subject: RE: [soa-blueprints] The Myth of ESB... is it a blueprint or a pattern...

We’re 2+ years into a production ESB implementation in my line of business, so I think I can speak with some authority on this one.


Writing services has become easier, but it’s still not easy.  Having an ESB and an associated team lets us approach services from a ‘center of excellence’ standpoint. 


No vendor has come up with good solutions to the challenge of versioning services.  Indeed, it’s very hard to write XML Schemas that version well – it’s a defect of the schema for schemas itself, not just a vendor gap (though it is that too).  So, our ESB gives us an opportunity to buffer our development teams against the thrash in the enterprise beyond.


Services are often delivered in “one size fits all” format.  An ESB is a chance for us, as one of many lines of business, to tailor that service to our own ends, adding caching or applying security and visibility restrictions.  This goes to Steve’s point about needing to assume that buses are >1 in number.


The ESB lets us forward responsibility for certain kinds of complexity.  If an enterprise service only provides a SOAP/HTTP interface, we can put an ESB service in front of it that does guaranteed delivery using JMS and then let the ESB be responsible for getting it through to the less-reliable interface.


The ESB is the natural place to implement fan-out of parallel service calls.  Multithreaded programming is hard enough that we don’t want most developers doing it.  Doing this sort of thing in the ESB lets it provide “value add” aggregating services that the enterprise will not cover.


Looking into my crystal ball, I think the next big push in this arena will be to virtualize ESBs.  Today, our ESB is a network-addressable endpoint with SLAs and the whole shooting match.  In a heterogeneous computing environment we’ll always need that to some extent, but it is reasonable to ask why we’d continue to incur the cost of network indirection for the ESB when we can just co-deploy.  Perhaps with the rise of ‘utility computing’ that will just “happen” in infrastructure and we won’t have to think about it.


Eric Friedman

Wells Fargo Private Client Services Architecture


From: Jones, Steve G [mailto:steve.g.jones@capgemini.com]
Sent: Monday, December 05, 2005 3:33 PM
To: soa-blueprints@lists.oasis-open.org
Subject: [soa-blueprints] The Myth of ESB... is it a blueprint or a pattern...



A question to the group


Back in the old “Enterprise Application Integration” days the vendors pushed a model which had either a single broker in the middle, or a bus in the middle.  The common element was always that “one” thing in the centre.  We are now seeing the same thing with ESB, the concept of a single bus (product) that rules the enterprise.  With EAI one of the biggest challenges was that product centric view of the world which led to organisations being left with “legacy” EAI which is as much of an issue as the applications it was meant to make easy to access (any Monk programmers out there?).


So what my strawman is to this group (and as the Soalogic thing evolves its quite important) is that concept of bus federation is essential to an SOA Blueprint, you must assume that there will be multiple busses, potentially at all levels, these may use similar technology (even identical) but the principles of federation should be the default for a well formed SOA.  Now is this a pattern or a blueprint, and if a blueprint where should it be considered.  My viewpoint is that there needs to be an official counterpoint to the vendor view that takes a Lord of the Rings (one ESB to find them all and in the darkness bind them) approach to delivery.  The best ESB is the one that assumes it isn’t the only thing around.






Steve Jones | Capgemini

CTO, Application Development Transformation

T +44 870 906 7026| 700 7026| www.capgemini.com

m: steve.g.jones@capgemini.com

txt: +44 (0) 7891157026

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