To me SOA has always been about the platform agnostic delivery of
information such that it can be reused within and across Enterprises. I
also believe that in the current state of technology, web services are
the best way of achieving this vision.
An essential pillar of making this real is Interoperability. At the
technology level, currently I am a more than a bit disheartend at the
lack of progress on the fundementals. Hopefully something will come out
of the conversations that are taking place on SOAPBuilders and the work
that is being done at W3C, as WS-I does not seem to be pushing the
envelope any.. Be that as it may, I mention it simply to set the context
for my question..
And that in particular relates to the concept of "Semantic Dissonance"
(I knew the concept, but first saw this particular phrase in the
"Integration Patterns" book from the Microsoft PAG). Quoting it "This
term describes a situation where data that appears to be the same may
not necessarily mean the same thing. For example, one system might treat
a monetary figure for annual revenues as if it includes sales tax, while
another system treats the monetary figure as if it does not include any
taxes. Likewise, one system might define the Western Region, in the
context of revenue breakdown, to include the state of Colorado.
Meanwhile, another system may define Colorado as part of the Central
Region."
In my community, which is diverse, distributed and global, an approach
that has been proposed is to establish communities of interest that work
to define common vocabularies to resolve this dissonance. The end result
of which would be encapulated in shared schemas that would be available
for use.
Another approach that has been articulated is the use of a Mediation
layer to provide Semantic Mappings between disparate systems. I belive
both approaches have value and should be applied judiciously, although I
shrudder whenever some of the more ardent proponents of the Mediation
apporach wave the Mediation-As-The-Magic-Wand-That-Solves-All. I
instinctively feel that one should keep the number of Intermediaries in
the message path as small as possible.. There is enough going on there
already..
Given that in any large Enteprise, this problem exists and as our SOA
based systems extend outside our firewalls the problem is only going to
get worse, what approaches exist, and what have and have not worked when
trying to solve this issue? In short, what has been the effectiveness
of the above approaches in your Enterprises? What were the pain-points?
Are there any other approaches that provided a better ROI?
Your thoughts and comments would be appreciated..
Regards,
- Anil
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