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Re: service references (was: Re: WSA diffs from REST)

From: Paul Prescod <paul@prescod.net>
Date: Mon, 23 Sep 2002 15:45:08 -0700
Message-ID: <3D8F9974.6050404@prescod.net>
To: Anne Thomas Manes <anne@manes.net>
CC: Sanjiva Weerawarana <sanjiva@watson.ibm.com>, Mark Baker <distobj@acm.org>, www-ws-arch@w3.org

Anne Thomas Manes wrote:
> Systinet WASP has supported service references for more than a year. It
> references a Web service by its WSDL port. To pass a service by reference,
> you return the URI of the WSDL port, and you return an instance ID of the
> service instance in a SOAP header. You can reconnect to the same instance by
> dynamically connecting to the service (using a dynamic proxy or a DDI) and
> specifying the instance ID in the SOAP header. The WSDL file for the service
> indicates what types and headers are used in the service.

I am curious why I must pass a URI and an instanceID to connect to a 
service instance rather than naming each service instance by a single 
resolvable URI as is done elsewhere on the Web?

Also, I'd like to hear more about the WSDL. Obviously it is trivial to 
make a WSDL where a complexType "PO" is repeated or made optional 
through a parent's content model:

<element name="purchase_orders">
   <complexType>
      <element name="po" minoccurs="0" maxoccurs="20">
         <sequence>...</sequence>
      </element>
   </complexType>
</element>

Can I similarly refer to *references* to purchase order *services* (or 
port types)?

 >...
> It would be nice to define a standard SOAP extension to accomplish services
> by reference, but I don't view it as a top priority. We had a discussion
> about service references on Apache axis-dev a while back, but it didn't go
> anywhere.

I objserve that an awareness of this issue is not widespread in the Web 
Services industry. Individual web service deployers invent one-off 
solutions (UDDIs, XPaths, handles) and because they do not yet care 
about interoperability BETWEEN web services, they see no problem with 
using home-grown solutions.

  Paul Prescod
Received on Monday, 23 September 2002 18:45:41 GMT

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