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Flexibility and resilience of Web Services

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  • sudharshang <sudharshang@yahoo.com>
    Hi, I am going through a Web Services book. It says that a Web Service is flexible and resilient. It also says that changes introduced to the Service do not
    Message 1 of 2 , Feb 12 12:44 PM
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      Hi,

      I am going through a Web Services book. It says that a Web Service is
      flexible and resilient. It also says that "changes introduced to the
      Service do not break Client's ability to use the service". I am
      really confused with this sentence. How can a Client be not affected
      if a Web Service changes its existing operations/methods or when new
      operations/methods are added to it ? Will the Web Service publish
      different WSDL documents for the changes it introduced ? Since XML is
      at the heart of Web Services, how does it absorb the changes in the
      Service ? Any pointers or suggestions will be greatly appreciated.

      Thanks & regards,
      Sudharshan Govindan
    • jim@ironringsoftware.com
      Govindan, IMO, You are *so* right to question this premise though the claims of a loosely coupled Service Oriented Architecture (SOA) are possible they aren t
      Message 2 of 2 , Feb 15 7:20 AM
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        Govindan,

        IMO, You are *so* right to question this premise though the claims of a
        loosely coupled Service Oriented Architecture (SOA) are possible they aren't
        guaranteed.

        But consider how far off you'd be without XML, WSDL and SOAP! These
        technologies provide a virtualization layer that allows some degree of
        resilience in the face of change. For example I can add an Operation to a
        PortType without breaking old clients. In other distributed technologies
        that operated in a more tightly coupled way even this was impossible.

        Versioning is an enormous mostly unaddressed problem - to be fair perhaps
        "recently" addressed is more accurate. You can achieve version
        compatibility in XML by designing your schemas to be extensible. Check out
        any of the WS-* schemas for example. They tend to provide open content
        models when their specific parts are described but are decorated with
        extensibility elements - like the <xsd:any> <xsd:anyAttribute>, substitution
        groups etc. The up shot is that the initial versions can be extended and
        ignored by older versions.

        This is a really hard problem...

        Jim


        > -----Original Message-----
        > From: sudharshang <sudharshang@...>
        > [mailto:sudharshang@...]
        > Sent: Wednesday, February 12, 2003 3:45 PM
        > To: soapbuilders@yahoogroups.com
        > Subject: [soapbuilders] Flexibility and resilience of Web Services
        >
        >
        > Hi,
        >
        > I am going through a Web Services book. It says that a Web Service is
        > flexible and resilient. It also says that "changes introduced to the
        > Service do not break Client's ability to use the service". I am
        > really confused with this sentence. How can a Client be not affected
        > if a Web Service changes its existing operations/methods or when new
        > operations/methods are added to it ? Will the Web Service publish
        > different WSDL documents for the changes it introduced ? Since XML is
        > at the heart of Web Services, how does it absorb the changes in the
        > Service ? Any pointers or suggestions will be greatly appreciated.
        >
        > Thanks & regards,
        > Sudharshan Govindan
        >
        >
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