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

From: Anne Thomas Manes <anne@manes.net>
Date: Mon, 23 Sep 2002 20:42:52 -0400
To: "Assaf Arkin" <arkin@intalio.com>, "Paul Prescod" <paul@prescod.net>
Cc: "Sanjiva Weerawarana" <sanjiva@watson.ibm.com>, "Mark Baker" <distobj@acm.org>, <www-ws-arch@w3.org>
Message-ID: <ECEDLFLFGIEENIPIEJJPIEIGCHAA.anne@manes.net>

True ... but an instance ID is just a label for an instance. There's no
reason why the instance ID can't conform to the format of a URI.

> -----Original Message-----
> From: Assaf Arkin [mailto:arkin@intalio.com]
> Sent: Monday, September 23, 2002 8:29 PM
> To: Paul Prescod; Anne Thomas Manes
> Cc: Sanjiva Weerawarana; Mark Baker; www-ws-arch@w3.org
> Subject: RE: service references (was: Re: WSA diffs from REST)
>
>
> You will find that this approach is quite common. For example, when you're
> updating a record in the database you open a connection to the database
> (service) and identify the record in the SQL statement. You can write the
> application to deal with records in any database if you keep a distinction
> between the record identifier and server identifier. You can also use
> identifiers that have business meaning, e.g. a purchase order number,
> employee number, etc.
>
> Yes, this doesn't look consistent with other aspects of the Web
> or the REST
> approach, that prefer that each entity have a unique address. But it does
> allow you to perform various operations on objects regardless of which
> service you are using. It could be http://myserver.com today,
> http://yourserver.com tomorrow, but you will always operate on the same
> purchase order.
>
> arkin
>
>
> 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 20:42:23 GMT

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