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RE: LC 76 - What makes a msg WS-A?

From: Rogers, Tony <Tony.Rogers@ca.com>
Date: Sat, 16 Jul 2005 05:29:52 +1000
Message-ID: <7997F38251504E43B38435DAF917887F40C5EA@ausyms23.ca.com>
To: "Winkler, Steve" <steve.winkler@sap.com>, "Martin Gudgin" <mgudgin@microsoft.com>, "David Orchard" <dorchard@bea.com>, "David Hull" <dmh@tibco.com>
Cc: "Katy Warr" <katy_warr@uk.ibm.com>, <public-ws-addressing@w3.org>
I'm beginning to think that we regard a message as being sent down the "this is a WS-A message" fork in the trail when it has an Action header, or another WS-A header with mustUnderstand set to true. Otherwise it goes down the "this is NOT a WS-A message" fork.
 
Agreed? Violently rejected?
 
Tony

	-----Original Message----- 
	From: public-ws-addressing-request@w3.org on behalf of Winkler, Steve 
	Sent: Fri 15-Jul-05 18:59 
	To: Martin Gudgin; David Orchard; David Hull 
	Cc: Katy Warr; public-ws-addressing@w3.org 
	Subject: RE: LC 76 - What makes a msg WS-A?
	
	
	 
	Hi Katy, 
	 
	Look what you started... ;-)
	 
	In sifting through the mails, I've gathered that: 
	 
	If the client expects that WS-A machinery is to be engaged on the endpoint to which they are sending, they need to include at least one wsa:Header with a mustUnderstand attribute set to true.  The receiving side needs to check if any of the wsa:Header elements defined in the specification are present with the mU attribute set to true, if so they need to process the message in accordance with the WS-A spec (this includes faulting if wsa:Action is not present, one reason why I wasn't happy with Gudge's original answer).  
	 
	Now for some questions:
	 
	Does this reflect an accurate understanding of the discussion up to this point?  
	If so, Katy, does this satisfy your original question?  
	Is the group satisfied with this summary?  
	Should we state something like this explicitly in the spec?
	 
	 
	Cheers,
	Steve
	 
	 
	-------------------------
	Steve Winkler 
	SAP AG
	 
	
	 

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		From: public-ws-addressing-request@w3.org [mailto:public-ws-addressing-request@w3.org] On Behalf Of Martin Gudgin
		Sent: Thursday, Jul 14, 2005 3:08 PM
		To: David Orchard; David Hull
		Cc: Katy Warr; public-ws-addressing@w3.org
		Subject: RE: LC 76 - What makes a msg WS-A?
		
		
		I thought it was clear too. And it fits with the SOAP processing model and so works for endpoints which were deployed long before WS-A was a twinkle in the eye of it's multiple parents...
		 
		Gudge


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			From: David Orchard [mailto:dorchard@bea.com] 
			Sent: 14 July 2005 22:32
			To: David Hull; Martin Gudgin
			Cc: Katy Warr; public-ws-addressing@w3.org
			Subject: RE: LC 76 - What makes a msg WS-A?
			
			

			I thought it was clear.  As soon as a single ws-a header is marked with mU, then a fault will be thrown if there are any missing headers like Action.  If there are no headers marked with mU and there are missing headers, then it's up to the receiver to decide whether to throw a fault or ignore all the ws-a headers.

			 

			Dave

			 

			 

			
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			From: David Hull [mailto:dmh@tibco.com] 
			Sent: Thursday, July 14, 2005 2:25 PM
			To: Martin Gudgin
			Cc: David Orchard; Katy Warr; public-ws-addressing@w3.org
			Subject: Re: LC 76 - What makes a msg WS-A?

			 

			Martin Gudgin wrote: 

			+1

			Am I correct in reading that as "we should throw a fault if there is a wsa:ReplyTo but no wsa:Action" and we're back on the same page?  I hope so, but when you say things like "I don't see why we want to mandate a fault in such a case." it seems like you're saying that we shouldn't (or at least shouldn't feel obliged to) throw a fault in such cases.
			
			Perhaps you could enumerate with which combinations of headers a WSA-compliant endpoint should and should not produce a fault?  We can then check that against the rules in section 3 and know whether we need to have any further discussion.
			
			

			 

			Gudge

				 

				
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				From: David Orchard [mailto:dorchard@bea.com] 
				Sent: 14 July 2005 22:03
				To: David Hull; Martin Gudgin
				Cc: Katy Warr; public-ws-addressing@w3.org
				Subject: RE: LC 76 - What makes a msg WS-A?

				It seems to me that you can't pick and choose which headers to support.  If there are any insufficient ws-a information (like contains a replyTo but no Action) then none of the ws-a processing can be invoked.  It's not a smorgasborg.

				 

				Dave

				 

				
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				From: public-ws-addressing-request@w3.org [mailto:public-ws-addressing-request@w3.org] On Behalf Of David Hull
				Sent: Thursday, July 14, 2005 1:41 PM
				To: Martin Gudgin
				Cc: Katy Warr; public-ws-addressing@w3.org
				Subject: Re: LC 76 - What makes a msg WS-A?

				 

				Martin Gudgin wrote: 

				I agree with your analysis of the three steps. I don't see why we want to mandate a fault in such a case. The client gets to decide whether he wants a fault or not based on whether he marks the header mU='true' or not...

				What would happen to the [reply endpoint] in this case (or rather, these cases, as mU may be true or not)?  Would it be used as a reply address?  Would it be silently ignored? Something else?
				
				In the first case, it seems strange to follow WSA rules but not complain about a missing mandatory header.  In the second case, it seems less than robust to silently ignore a field that would otherwise have a significant effect on processing.
				
				Not sure about the third case.
				
				
				

				 

				Gudge

					 

					
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					From: David Hull [mailto:dmh@tibco.com] 
					Sent: 14 July 2005 21:21
					To: Martin Gudgin
					Cc: Katy Warr; public-ws-addressing@w3.org
					Subject: Re: LC 76 - What makes a msg WS-A?

					Martin Gudgin wrote: 

					Well, one could argue that the endpoint that accepts WS-A messages and the one that accepts non-WS-A message are not actually the same endpoint despite the fact that they're listening on the same URI, I suppose...

					Sure, but the multiplexing still has to be done one way or another.
					
					
					

					 

					I'm still not seeing why the endpoint can't use the following sequence of steps;

					 

					1.    Does the message contain a wsa:Action header?

					2.    If the answer to question 1. is 'Yes' then look for other wsa: * headers and populate abstract properties as appropriate.

					3.    If the answer to question 1 is 'No' then process the message using normal SOAP rules (including raising mU faults if there are any other wsa:* headers marked mU='true' )

					That will not produce a fault if a message contains an explicit wsa:ReplyTo (with no mU) but no wsa:Action, right?  The test in step 1 fails and we go straight to step 3.  So it's OK iff we don't want a fault in such a case.  My understanding is we do want a fault in such a case.
					
					
					

					 

					Gudge

					 

					
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					From: David Hull [mailto:dmh@tibco.com] 
					Sent: 14 July 2005 20:58
					To: Martin Gudgin
					Cc: Katy Warr; public-ws-addressing@w3.org
					Subject: Re: LC 76 - What makes a msg WS-A?

					Martin Gudgin wrote: 

					Why is it a problem if a message which doesn't have wsa:Action in it is NOT subject to 'validation' (what does that mean, BTW) by the receiver?

					Yeah, I'm not comfortable with the terminology either.
					
					The question is, should a WSA compliant endpoint throw a fault if it gets a message with (say) a [reply endpoint] and no [action]?
					
					If I understand right, you're saying that (straightforwardly), it should.  That's certainly how I'd interpret the current core.
					
					Section 3 (specifically section 3.1) says that [action] is required (i.e., its cardinality is (1..1)), so the only question (and the one I think Katy was asking) is, when does section 3 apply?
					
					There appears to be consensus that endpoints should be able to accept both old-style and new-style requests without problem.  This means that such an endpoint must be prepared to accept messages with no wsa: headers at all -- contrary to as strict reading of section 3.  In particular, such an endpoint should not fault if wsa:Action is absent unless other wsa: headers are present.  In such a case, section 3 does not apply universally, and we want to be able to say when it does and doesn't apply.
					
					So what's the best way to say this?  We can't use abstract properties, since they may be defined even if there are no wsa: headers in the incoming message.  So we have to look at the incoming infoset.  In short, an endpoint capable of handling both styles should apply the constraints in section 3 if the incoming SOAP message contains any wsa: headers, and should follow the pre-WSA behavior otherwise.  This is fine as long as the underlying transport binding doesn't synthesize wsa: headers that aren't explicitly there.  Otherwise, we'd need some other way of figuring out if the sender meant to use WSA.
					
					Does that make more sense?  I believe this is a long-standing and thoroughly discussed issue.  If you were thinking of something else, let's sort that out first.
					
					
					

					
					Gudge

					 

					
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					From: David Hull [mailto:dmh@tibco.com] 
					Sent: 14 July 2005 20:29
					To: Martin Gudgin
					Cc: Katy Warr; public-ws-addressing@w3.org
					Subject: Re: LC 76 - What makes a msg WS-A?

					Martin Gudgin wrote: 

					OK, I'm confused.

					 

					Why do you conclude that the answer to my question "Given that the wsa:Action header is mandatory, isn't it the presence of that header?" is 'No'. 

					 

					I would have come to the opposite conclusion;

					 

					I have an endpoint that understands WS-Addressing. It receives a message that contains wsa:ReplyTo but no wsa:Action. It generates a fault. Seems pretty straightforward to me.

					Sure.  That is a perfectly straightforward rule.  In fact, it's implied by what we say in section 3.3.
					
					I thought you were trying to answer the question "When is an incoming message deemed to be a WS-Addressing message and therefore subject to the appropriate WS-Addressing validation?" with (rephrasing the reply as a statement) "It's subject to WSA validation if the wsa:Action header is present."  And of course, this clearly won't work, since it specifically doesn't try to validate a message with wsa:ReplyTo and no wsa:Action.
					
					If you meant something else, then never mind.  It's probably not worth sorting.
					
					
					

					 

					I have an endpoint that doesn't understand WS-Addressing. It receives a message that contains one or more wsa: headers, it either ignores them or generates a mustUnderstand fault depending on whether those headers are marked mustUnderstand='true' or not. Again, seems pretty straightforward to me.

					Sure.  As I said, we're talking about behavior of endpoints, not properties of messages.
					
					As DaveO says, the interesting case is that of an endpoint that wants to accept non-WSA messages without complaint but also handle WSA messages properly.
					
					
					

					 

					Gudge

					 

					
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					From: David Hull [mailto:dmh@tibco.com] 
					Sent: 14 July 2005 18:02
					To: Martin Gudgin
					Cc: Katy Warr; public-ws-addressing@w3.org
					Subject: Re: LC 76 - What makes a msg WS-A?

					Martin Gudgin wrote: 

					 

					 

					
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					From: David Hull [mailto:dmh@tibco.com] 
					Sent: 14 July 2005 16:32
					To: Martin Gudgin
					Cc: Katy Warr; public-ws-addressing@w3.org
					Subject: Re: LC 76 - What makes a msg WS-A?

					Is this really a question of how to support both WSA and old-style HTTP requests on the same endpoint?  
					[MJG] I don't know, I didn't ask the original question.

					Hmm ... my message was in-reply-to yours, but the question was really aimed more at Katy.  Maybe we need BPEL here :-).
					
					
					

					
					  I.e., if I don't see any WSA headers at all, I assume it's an old-style request and act accordingly, but if I see anything WSA, I follow the rules in section 3? 
					[MJG] I guess one could do that... 

					Well, one should do something to ensure that old-style requests are accepted as such.
					
					
					

					
					The tricky bit is that, since MAPs like [destination] and [reply endpoint] can default, a message with no wsa: elements on the wire could still be assigned values for some of its MAPs, since the infoset will still have values for the corresponding elements. 

					[MJG] Which Infoset are you talking about? The XML Infoset has no such values.

					Sorry, I didn't get that quite right.  I was going by section 3.2, particularly the descriptions of wsa:To:

					This OPTIONAL element (whose content is of type xs:anyURI) provides the value for the [destination] property. If this element is NOT present then the value of the [destination] property is "http://www.w3.org/@@@@/@@/addressing/anonymous" <http://www.w3.org/@@@@/@@/addressing/anonymous> .

					
					(and similarly for wsa:ReplyTo). I initially misread this as stating that the element defaulted, as opposed to the MAP.  So s/since the infoset will still have values for the corresponding elements/since the properties are defaulted in the absence of the corresponding elements in the infoset/.  This sort of confusion could be seen as an argument against the two-layered approach (or simply as an argument that I read too quickly).
					
					In any case, you can't simply look at the abstract properties and say "some WSA properties are defined, so it's a WSA message".
					
					
					

					
					   So either we have to drop down to look at the infoset level, and in particular at the non-defaulted elements in the infoset, or we have to find some marker that can't be defaulted away.  This is why the [action] property looks significant here.  But on the other hand, what if I include a wsa:ReplyTo element and no action?  By the "it's WSA iff [action] is present" rule, that's not a WSA message and therefore not an error.  This seems wrong. 
					[MJG] Why does it seem wrong?

					It seems wrong not to fault for a message that contains a wsa:ReplyTo on the wire but not a wsa:Action.
					
					
					

					
					Put another way, when would one get a fault for omitting [action]? 
					[MJG] Whenever another wsa: header is present in a message.

					In other words, the answer to your question ("Given that the wsa:Action is mandatory, isn't it the presence of that header?") is "No."
					
					This is why at the Berlin meeting we tried to make sure that all the possibilities were covered for various combinations of the MAPs.  I believe we've satisfied ourselves that they are, but perhaps we need to revisit this work?
					
					
					

					
					
					Martin Gudgin wrote: 

					Given that the wsa:Action is mandatory, isn't it the presence of that header?

					 

					Gudge

					 

					
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					From: public-ws-addressing-request@w3.org [mailto:public-ws-addressing-request@w3.org] On Behalf Of Katy Warr
					Sent: 14 July 2005 16:07
					To: public-ws-addressing@w3.org
					Subject: LC 76 - What makes a msg WS-A?

					
					Please could we discuss the following in the context of LC76? 
					
					When is an incoming message deemed to be a WS-Addressing message and therefore subject to the appropriate WS-Addressing validation?   Is it based on the presence of any WS-addressing Message Addressing Property?  For example, does a message containing a reference parameter (but no other WS-Addressing information) need to result in a MessageAddressingHeaderRequired?    Or, for example, does the declaration of the wsa namespace rendor the message WS-Addressing? 
					
					Thanks 
					Katy

					 

					 

					 

					 

					 

				 

			 
Received on Friday, 15 July 2005 19:30:10 GMT

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