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Section 2.3 - examples

From: Glen Daniels <gdaniels@sonicsoftware.com>
Date: Sun, 13 Mar 2005 21:07:47 -0500
Message-ID: <80A43FC052CE3949A327527DCD5D6B27E5AA82@MAIL01.bedford.progress.com>
To: <public-ws-addressing@w3.org>

In fulfillment of my AI from the face-to-face in Boston, here is a first
cut at some example text to go after the new text for sec 2.3.  This
gets the basic idea across but likely needs some wordsmithing/honing:

-------------------

The following examples serve to illustrate both the flexibility inherent
within the EPR concept and a bit more detail into the meaning of the
above paragraph.

For the first example, assume two different web service clients receive
the following EPR as a result of some interaction (for instance each
processing a SOAP response message):

<wsa:EndpointReference>
  <wsa:Address>http://example.com/MessageBroker</wsa:Address>
</wsa:EndpointReference>
[caption - Example 1 EPRs 1 and 2]

Despite the fact that these two EPRs are lexically identical, in this
particular circumstance the EPRs may not in fact point to the same web
service - for instance, the endpoint at the wsa:Address URL might be a
message broker whose purpose is to provide a single outward-facing
address which fronts many individual services behind the scenes.  The
actual service which is referenced might be determined by contextual
information about the clients in question, including session state or
even the client's network address.  So in this case, two EPRs which
might appear to be "the same" are in fact not necessarily so.

Our second example involves two EPRs which are lexically very different:

EPR1:
<wsa:EndpointReference>
  <wsa:Address>http://example.com/Service1</wsa:Address>
  <wsa:ReferenceParameters>
    <cookie>chocolate-chip</cookie>
  </wsa:ReferenceParameters>
  <myExt:UUID>56433-4553-6927</myExt:UUID>
</wsa:EndpointReference>

EPR2:
<wsa:EndpointReference>
  <wsa:Address>mailto:Service1@mail.example.com</wsa:Address>
  <myExt:UUID>56433-4553-6927</myExt:UUID>
</wsa:EndpointReference>
[caption - Example 2 EPRs 1 and 2]

As you might surmise, we can imagine situations where these very
different-seeming EPRs are in fact interchangeable - but the fact that
they have this quality can only be known by using additional
information, such as the fact that the <myExt:UUID> EPR extension
indicates a token identifying the "service ID" and that matching service
IDs mean interchangeable EPRs.  This example demonstrates an example
mechanism for determining EPR "sameness" which might layer on top of
this specification.

------------------

Thanks,
--Glen
Received on Monday, 14 March 2005 02:08:09 GMT

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