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RE: LC124

From: Arthur Ryman <ryman@ca.ibm.com>
Date: Thu, 7 Jul 2005 08:05:15 -0400
To: <paul.downey@bt.com>
Cc: www-ws-desc@w3.org, www-ws-desc-request@w3.org
Message-ID: <OF006B38E0.9AD349E0-ON85257037.0040AEF7-85257037.0042655D@ca.ibm.com>
Paul,

1) I am very much in favour of the intention behind this proposal since 
this is a real customer problem. But we do need to look at the details.

2) Let me explain more. I am concerned that there is no normative 
description of what "ignoreUnknowns" means. I understand that there are 
algortihms and data binding implementations that exhibit this behavior, 
but they are proprietary. What assurance do we have that they will 
interoperate? For example, vendor A may be very lenient and accept some 
unknown content, while vendor B may reject it interpretting it as a schema 
violation. Pointing to implementations and conference papers is not good 
enough. That is the point of the SOAP encoding example. We owe it to the 
community to reference a normative spec that defines ignoreUnknowns. Is 
there one? The latest proposal talks about ignoreUnknowns but doesn't 
define it precisely.

3) You may be happy enough that old Web services don't break when they get 
unknown content, but that is just one use case. Yes, we are encroaching 
into the domain of semantics, but Web services are not an abstract 
exercise. They exist to implement semantics. Web services are more than 
just interface. Yes, WSDL should only describe interface. That should tell 
you this is a bigger problem and that WSDL alone can't solve it. We need a 
coordinated effort across all the aspects of Web services. I agree that 
WSDL 2.0 should at least enable versioning. But the current proposal goes 
too far by being part of the Core and by making this, IMHO non-normative, 
definition the default. Can't we at least induce the Schema WG to create a 
Note that applies to XSD 1.0?

4) As I said, I still don't see a normative definition of ignoreUnknowns 
that would ensure interoperability.


Arthur Ryman,
Rational Desktop Tools Development

phone: +1-905-413-3077, TL 969-3077
assistant: +1-905-413-2411, TL 969-2411
fax: +1-905-413-4920, TL 969-4920
mobile: +1-416-939-5063, text: 4169395063@fido.ca
intranet: http://labweb.torolab.ibm.com/DRY6/



<paul.downey@bt.com> 
Sent by: www-ws-desc-request@w3.org
07/07/2005 07:24 AM

To
Arthur Ryman/Toronto/IBM@IBMCA, <www-ws-desc@w3.org>
cc

Subject
RE: LC124







Arthur,

thanks for taking the time and trouble to discuss this issue 
and in trying to gain a company position within IBM. 

I'll try and answer the discussion points raised:

1) Agreed, obviously! Enabling the description of Web 
   services that evolve is likely to be our top reason to 
   move towards using WSDL 2.0. 

2) Agreed, in essence this is an XML Schema issue, hence our 
   original efforts to engage the Schema WG in a joint Task Force 
   for versioning. However, Web services has a strong and simple 
   use case for evolution of messages and much of the current focus 
   of work on versioning within XML Schema has been in gathering 
   other use-cases targeted at XML Schema 1.1

   The cautionary tale regarding SOAP encoding is a good example, 
   however that was a far more radical change than this proposal
   and predated the XML Schema Recommendation.
   ignoreUnkowns allows continued use of a current schema processor 
   for validation, whilst embodying current best practice exhibited 
   by the more flexible data binding implementations.

3) This is an interesting point, but one which does fall into the 
   semantics of the additional content:

   If a processor requires the additional content, or that additional
   content changes the meaning of existing content, then it isn't
   a backwards compatible change, and should be published as a new
   message, operation, service, etc.

   The boolean flag enables publishers to add and accept additional
   content, or highlight that strict validation should be used to 
   constrain the message contents. I'm not sure what more information
   would be useful, without exposing 'semantics', something
   we avoid in WSDL.

4) Please see the latest proposals for text:
   http://lists.w3.org/Archives/Public/www-ws-desc/2005Jun/0097.html 


Paul


-----Original Message-----
From: www-ws-desc-request@w3.org [mailto:www-ws-desc-request@w3.org]On 
Behalf Of Arthur Ryman
Sent: 06 July 2005 23:33
To: www-ws-desc@w3.org
Subject: LC124



I've been discussing LC124 with my colleagues and I thought I'd post an 
update in case we discuss this tomorrow. 

1. In general, we agree the versioning is important, and we'd like the 
problem addressed. 
2. We are concerned that this is really an XML Schema problem and that 
WSDL is probably not the right place to address it. There is work going on 
now in the Schema WG. There are several solutions being proposed and it 
would be premature for WSDL to adopt the validate-twice solution (although 
that is a strong contender). As a cautionary tale, the creative use of 
Schema with SOAP Encoding was cited. The schema didn't really describe the 
message. We don't want a repeat in WSDL 2.0. We are concerned about 
locking in a solution that may not agree with the direction of Schema. 
3. The boolean nature of ignoreUnknowns is not very useful. In many 
scenarios, it is important to know if the unknown content is preserved 
(e.g. passed on) or even processed. 
4. There is no normative document that describes the proposed processing 
algorithm. Who will write that? (pointing to conference papers is not 
adequate). The WSDL spec should only cite other specs for Core features. 

I need more time to establish a company position since this is vacation 
season. I'll try to move this issue forward though. 


Arthur Ryman,
Rational Desktop Tools Development

phone: +1-905-413-3077, TL 969-3077
assistant: +1-905-413-2411, TL 969-2411
fax: +1-905-413-4920, TL 969-4920
mobile: +1-416-939-5063, text: 4169395063@fido.ca
intranet: http://labweb.torolab.ibm.com/DRY6/
Received on Thursday, 7 July 2005 12:05:34 GMT

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