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RE: On WSDL attributes

From: Martin Chapman <martin.chapman@oracle.com>
Date: Tue, 9 Sep 2003 14:02:20 -0700
To: "'Steve Graham'" <sggraham@us.ibm.com>, "'Savas Parastatidis'" <Savas.Parastatidis@newcastle.ac.uk>
Cc: "'WS Description List'" <www-ws-desc@w3.org>, <www-ws-desc-request@w3.org>, <public-ws-desc-state@w3.org>
Message-ID: <011101c37715$ab9a2390$1faf2382@us.oracle.com>

Steve,
Properties in BPEL are very different than attributes defined by OGSI.
A BPEL property relate to portions of a message and is not a queryable 
"feature" of a web service itself.

Cheers,
 Martin. 

> -----Original Message-----
> From: www-ws-desc-request@w3.org 
> [mailto:www-ws-desc-request@w3.org] On Behalf Of Steve Graham
> Sent: Tuesday, September 09, 2003 5:03 AM
> To: Savas Parastatidis
> Cc: WS Description List; www-ws-desc-request@w3.org; 
> public-ws-desc-state@w3.org
> Subject: Re: On WSDL attributes
> 
> 
> 
> 
> 
> 
> 
> Savas:
> We continue to debate the merits for this work.  We have 
> constituencies in the Systems Management space (OASIS WSDM 
> TC) and Grid (OGSI) that clearly need the notion of 
> attributes in WSDL.  We do not believe the concept is limited 
> to those two domains, the concept is much broader than that.
> 
> We agree that a Web service fundamentally is about message 
> exchanges.  The attribute work defines additional information 
> that helps the requestor form these messages, by indicating 
> what sort of information can be the subject of the get and 
> set operations. Furthermore, it does this in such a way that 
> allows more powerful interfaces (such as OGSI service data 
> operations) to be defined to reuse the base information 
> provided by the attribute declaration mechanism.
> 
> You claim that attributes are not a concept in the WSA.  
> However it is true that they are not FORBIDDEN by WSA.  This 
> extension is needed for Grid and Systems management, and may 
> be quite useful in other spaces.  BPEL has properties for 
> example, that appear to be a similar concept, would it not be 
> better if  we all used the same mechanisms for 
> properties/attributes etc? We agree that attributes in WSDL 
> does not exist, we are proposing, based on our experience in 
> Grid and Systems management that it be added.
> 
> The notion that the work in MEPs is sufficient and precludes 
> the work for attributes is misguided.  We proposed some 
> simple access mechanisms to suggest how bindings treat 
> attributes in an analogous way to operations. The MEPs work 
> does not reduce the need for attributes.
> 
> We continue to disagree about the relationship between 
> objects and SOA. Object orientation is an implementation 
> concept.  There is nothing in SOA that precludes an 
> object-orientation or a non-object orientation.
> 
> Of course, we could always use extensibility to support 
> attributes, in fact this what OGSI does today with 
> serviceData.  However, it was deemed appropriate, by several 
> constituencies to try to standardize attributes in the core language.
> 
> sgg
> 
> ++++++++
> Steve Graham
> sggraham@us.ibm.com
> (919)254-0615 (T/L 444)
> STSM, On Demand Architecture
> ++++++++
> 
> 
> 
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>                       <Savas.Parastatidis@newca        To:    
>    "WS Description List" <www-ws-desc@w3.org>                 
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>                       stle.ac.uk>                      cc:    
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>                       09/09/2003 07:43 AM                     
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> 
> All,
> 
> Here are some thoughts by Jim Webber and myself on the 
> introduction of attributes in WSDL...
> 
> 
> The proposal on the introduction of attributes in the WSDL 
> specification has come a long way due to the work that the 
> relevant Task Force has produced. The most recent update to 
> the proposal is, we believe, closer to the WSDL way of 
> describing message exchanges. However, it is so close that we 
> believe attributes are not necessary for WSDL.
> 
> 1. Attributes represent a concept that it is not part of the 
> Web Services Architecture. Nowhere in the WSA document, to 
> our knowledge, is it suggested that a Web Service has 
> attributes. Web Services send and receive messages. They do 
> not have operations, functions, methods, or attributes as it 
> is the case with object-based component models. WSDL is used 
> to describe messages that can be sent and received. The 
> notion of an "attribute" attempts to add a characteristic to 
> Web Services that simply does not exist.
> 
> 2. The current version of the proposal defines particular 
> message exchange patterns. Since there is already work being 
> carried out in this area, we feel that there is no need for 
> the introduction of attributes in WSDL. For instance, the 
> notion of a solicit-response MEP is somewhat analogous to 
> "getting" an attribute, while a request-only MEP is analogous 
> to "setting" an attribute. Given these abilities which are 
> already an accepted part of WSDL, this undermines the need 
> for "read", "read-write", and "write" qualifiers for attributes.
> 
> To summarise: We believe that attributes are a fundamental 
> property of object-based systems, and do not have a 
> corresponding use in SOA. We are supported by WSA in this 
> thinking. Furthermore, we believe that the benefits of an 
> attribute style interaction in terms of being able to "set" 
> or "get" structured XML data from a Web service is already 
> supported with WSDL operations.
> 
> While we think that the work of the ATF is correct in itself, 
> we would oppose the inclusion of such work into WSDL, and 
> would instead anticipate that it would form part of some 
> other specification which leverages WSDL extensibility. Those 
> communities which have a demonstrated need to deploy Web 
> services in a distributed object-like scenario (e.g. Grid), 
> can then utilise the separate attribute specification to 
> support their needs, without adding non-WSA features to WSDL.
> 
> Regards,
> Jim Webber
> Savas Parastatidis
> 
> 
> 
> 
> 
Received on Tuesday, 9 September 2003 17:02:47 GMT

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