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Document Control by chenshu

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									Document Control
Versio       Details                                                                                          Changed                Date
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0.1          Initial Revision                                                                                 BC                     28/Feb/2007




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 This document is protected by copyright and the information contained herein is confidential. The document may not be copied and the information herein
 may not be disclosed except by the written permission of, and in a manner permitted by the proprietors, Westinghouse Rail Systems Australia Limited, 2007.
Application Integration

A five-ten minute presentation by
Benjamin Carlyle
The two Webs?

   The World-Wide-Web
   Enterprise Web Services




                              3
The two many Webs!

   The World-Wide-Web
   My Industry’s Web
   My Supply Chain’s Web
   My Enterprise’s Web
   …
   Thousands of them!




                            4
Each with…

   Hierarchy/Overlap
       Components may participate in several Webs
   Special interaction patterns
       Special protocols, document types and methods
       More than just request/response message exchanges?
   Separate application of Metcalfe’s law
       A particular web can be defined as a set of components
        that implement the same uniform interface
       Components that can’t understand each other don’t get
        network effects
       Smaller Web = Lower Intrinsic Value.


                                                                 5
Web Services are too Low-Level

   HTTP is an application-level protocol
   SOAP needs a specific WSDL added to be an
    application-level protocol
   Each new WSDL = A new web
   How to we minimise the number of WSDL?
   How do we see WSDLs evolving?




                                                6
REST Covers many of these issues

   If a parent web has an appropriate interaction
    pattern, use it
     No web-specific code needs to be written
     Avoid proliferation of webs – text/plain
   If a parent web has a nearly-appropriate interaction
    pattern, embrace and extend
     Add new methods as required – SUBSCRIBE
     Add new content types – purchase order, train list.
   Evolution by different webs influencing each other
     What is special today might not be tomorrow
                                                            7
Each web needs

   A registry of
     Methods,
     return codes,
     content types,
     other interaction-affecting features
     All of which are understood when appropriate by all
      components
   References to parent web registries
   Can WSDL or WADL help make this machine
    readable: Reduce cost of low-value webs.

                                                            8
Recommendation

   WS-*/HTTP/WAKA/whatever?
     In the short term, use bridges to make everything talk
     Define a high-fidelity “HTTP” WSDL that services can
      implement
     In the longer term, a single protocol should rule them
      all
     HTTP has enough momentum to see any challenger
      wash away. Can it be extended, rather than replaced?
   Focus on content-type development and filling in
    missing features such as pub/sub, HA, and MOM
    features
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