Good points. I hope I didn't come across as defending ESBs. I agree that they are not sufficient by themselves just as WSM and XML gateways are not sufficient by themselves.
Your points about the limitations of "most ESBs" seem like reasonable evaluation points to consider to be weighed against the positives. One side trip: programming vs declarative policies arguments always seem to assume "programming bad, policy definition/configuration good." This isn't always the case. Defining declarative policies can be just as complex as programming (one could argue that defining declarative policies is a form of programming) and can be just as damaging when errors are made. "...then you shouldn't need to do a whole lot of semantic, syntactic, or protocol mediation." I think we agree in principle on this, but we might disagree on how much of this type of mediation will be needed in practice--now and in the future. -Rob --- In [email protected], "Anne Thomas Manes" <[EMAIL PROTECTED]> wrote: > > Mediation is the "right" way to resolve semantic, syntax, protocol, > and other differences between service endpoints -- but: > > 1- an ESB is not necessarily the best solution to perform mediation. > For one thing, most ESBs aren't capable of performing security > mediation (enabling seamless federation across security domains). > For another thing, many ESBs tend to be a bit "heavy" (e.g., > deployed in an app server). For a third thing, very few ESBs give > you the ability to configure the mediation using declarative > policies -- there's always a little programming involved. And > fourth, ESBs don't provide as much instrumentation as you'd like > for management and root cause analysis, and they're not really good > at managing SLAs. As a general rule, I prefer to use WSM or XML > gateways over ESBs for mediation and policy enforcement. (See later > in this message for a disclaimer regarding ESBs that aren't > like "most ESBs".) > > 2- (and this point goes back to integration vs disintegration) If > you are truly refactoring your systems rather than just integrating > application silos, then you shouldn't need to do a whole lot of > semantic, syntactic, or protocol mediation. > > You will need to do security mediation and policy enforcement, but > you shouldn't need to do a whole bunch of message and protocol > transformations. Again -- WSM and XML gateways are better at doing > security mediation and policy enforcement than ESBs.
