- From: Sanjiva Weerawarana <sanjiva@watson.ibm.com>
- Date: Tue, 17 Jun 2003 12:55:13 +0600
- To: "Savas Parastatidis" <Savas.Parastatidis@newcastle.ac.uk>, "Steve Graham" <sggraham@us.ibm.com>
- Cc: "David Snelling" <d.snelling@fle.fujitsu.com>, "Jim Webber" <jim.webber@arjuna.com>, <ksankar@cisco.com>, "Paul Watson" <Paul.Watson@newcastle.ac.uk>, <public-ws-desc-state@w3c.org>, "Steve Tuecke" <tuecke@mcs.anl.gov>, "Umit Yalcinalp" <umit.yalcinalp@oracle.com>
What you're proposing looks like the same approach BPEL took with properties - they are carried as part of the <message> and the definition tells you where to find it in the message. Interesting. I have to think about this more. Sanjiva. ----- Original Message ----- From: "Savas Parastatidis" <Savas.Parastatidis@newcastle.ac.uk> To: "Steve Graham" <sggraham@us.ibm.com> Cc: "David Snelling" <d.snelling@fle.fujitsu.com>; "Jim Webber" <jim.webber@arjuna.com>; <ksankar@cisco.com>; "Paul Watson" <Paul.Watson@newcastle.ac.uk>; <public-ws-desc-state@w3c.org>; "Steve Tuecke" <tuecke@mcs.anl.gov>; "Umit Yalcinalp" <umit.yalcinalp@oracle.com> Sent: Tuesday, June 17, 2003 6:27 AM Subject: RE: Some requirements > > > > > Savas: > > Ok, things are getting more clear, but I still do not see your point. > > > > :-) and :-( > > > In your example, how do I as a requestor know how to get/set the value > of > > myAttribute? how can I query whether the state of the service has > > myAttribute="someValue" and anotherAttribute > 12 and ...? > > > > OK. This is not an example that I have thought through well nor it is a > proposal on how attribute should be presented in WSDL... just a vehicle > for discussion (I hope). > > An attribute is associated with a wsdl:message. A wsdl:message > indirectly provides the type of the attribute. > > <message name="msgName" > type="xsd:positiveInteger"/> > > <interface> > <operation name="getValue"> > <output message="msgName"/> > </operation> > > <attribute name="myAttribute"> > <output message="msgName"/> > </attribute> > </interface> > > In the above example, the attribute is readonly (no input message). > Unlike an operation, an attribute may have 0 to 1 output and 0 to 1 > input messages (if it has 0 and 0 it can be considered as static). > > An alternative representation with the same semantics could be: > > <attribute name="myAttribute" > message="msgName" > readonly="true"/> > > (Only allows a message "msgName" to travel from the service to the > consumer and not the other way around). > > Please note that the above example says nothing about the binding of the > attribute construct to an underlying communications protocol, exactly as > it is the case with operations. > > Attributes can have static values, like in OGSI (Note, no input or > output messages, so you need a type): > > <attribute name="myAttribute" type="xsd:positiveInteger"> > <input/> > <output/> > <value> > 1 > </value> > </attribute> > > You get the value of an attribute when you receive a message "msgName" > (how the "get 'myAttribute'" request is made to the service is > binding-specific). > > In the same way, you set the value of an attribute by sending a "set > 'myAttribute'" request, which, again, is binding-specific. > > WSDL says nothing about these requests, as it says nothing about how an > operation is mapped to a specific communications protocol. > > You see, however, such an approach does not require wsdl:operation > declarations, while the serviceData model does. Of course, there are > restrictions... No common way to dynamically created attributes, no > service-side queries. IMHO, these are facilities that should be > introduced by another specification (e.g., WS-ServiceData). WSDL just > introduces the syntax of an attribute and how it maps to messages. > WS-ServiceData may define what kind of wsdl:operations must be supported > by a web service that adheres to that spec. > > > > If one somehow associates attributes with messages, does the requestor > > somehow have to figure out which operations somehow use those messages > as > > input and output? > > > > I guess I still don't understand the approach you are suggesting, nor > do I > > completely understand your concerns with the OGSI service data > approach. > > > > I want to make it clear that I have no problems with the OGSI approach. > It works fine for what it is meant to address. It is defined by a > specification that meets the requirements of an application domain. Now, > you argue that serviceData, as defined by OGSI, can be useful not only > to the Grid application domain but in general to all application domains > in Web services. Again, I agree that this may be the case. However, I > believe that the serviceData concepts cannot be defined as is in WSDL > because they require the use of specific wsdl:operations. > > WSDL could be used to define how attributes can be made part of an > interface (as in the example above). Once you have that, you can build, > in a separate specification, the extra operations (wsdl:operations) that > are required. > > Just my 2c (or 2p since I am in the UK :-), > .savas. >
Received on Tuesday, 17 June 2003 02:55:15 UTC