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

From: Martin Gudgin <mgudgin@microsoft.com>
Date: Thu, 14 Jul 2005 13:15:45 -0700
Message-ID: <DD35CC66F54D8248B6E04232892B633806574DAD@RED-MSG-43.redmond.corp.microsoft.com>
To: "David Hull" <dmh@tibco.com>
Cc: "Katy Warr" <katy_warr@uk.ibm.com>, <public-ws-addressing@w3.org>
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...
 
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' )
 
Gudge


________________________________

	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


________________________________

			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


________________________________

				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: 

				 


________________________________

				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


________________________________

				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 Thursday, 14 July 2005 20:17:22 GMT

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