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

From: Winkler, Steve <steve.winkler@sap.com>
Date: Fri, 15 Jul 2005 01:59:29 -0700
Message-ID: <55620CF891864D4984A16302E4C420AA454610@uspale20.pal.sap.corp>
To: "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>
 
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
 

 

________________________________

	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


________________________________

		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

		 

		 

		
________________________________


		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

			 

			
________________________________


			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

			 

			
________________________________


			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

				 

				
________________________________


				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

				 

				
________________________________


				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 Friday, 15 July 2005 09:00:06 GMT

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