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Re: i009 - mustIgnore rule for multiple To, ReplyTo, etc.

From: Doug Davis <dug@us.ibm.com>
Date: Wed, 12 Jan 2005 20:55:17 -0500
To: tom@coastin.com
Cc: paul.downey@bt.com, public-ws-addressing@w3.org, tim@mindreef.com
Message-ID: <OF70AF17A6.AD779885-ON85256F88.000A3E71-85256F88.000A8ED2@us.ibm.com>
I feels a bit odd to me to count on other WS specs to define WSA 
semantics.  Having them define the extension elements and attributes along 
with their semantics, yes, but possibly redefine the semantics of base WSA 
elements, no.  WSA should either allow or disallow multiple instances - 
and define clearly what it does allow.

Tom Rutt <tom@coastin.com> 
Sent by: public-ws-addressing-request@w3.org
01/12/2005 05:28 PM
Please respond to

tim@mindreef.com, public-ws-addressing@w3.org
Re: i009 - mustIgnore rule for multiple To, ReplyTo, etc.

I think that extensibility would require that the spec state something 

"This spec does not define behaviour upon use of more than one instance 
of a ws:addressing header in a message".

Other specs , using ws addressing, could add their own semantics in the 
context of their use.

Tom Rutt

paul.downey@bt.com wrote:

>Hi Tim!
>from my POV helpful expert comments like yours and Noah's are always 
>and has to be one of the main reasons why a WG uses a public list for 
>You've raised some interesting points here and. Doug Davis also raised 
the targeted 
>role issue offline, so you're not alone with your concerns.
>In many respects the difficulties you raise around allowing multiple 
instances of a 
>should come as no surprise to me given the explosion of complexity was 
>main reason my raising this issue in the first place. i guess it possibly 
serves me 
>right for looking for an easy way out! i'll noodle on this a little more 
before our 
>discussion on this issue next week.
>                -----Original Message----- 
>                From: public-ws-addressing-request@w3.org on behalf of 
Tim Ewald 
>                Sent: Wed 12/01/2005 19:55 
>                To: Downey,PS,Paul,XAGA C 
>                Cc: public-ws-addressing@w3.org 
>                Subject: RE: i009 - mustIgnore rule for multiple To, 
ReplyTo, etc.
>                Paul,
>                Like Noah, I'm not a member of the WSA group, so feel 
free to tell me to go
>                away (unlike Noah I didn't add this disclaimer to earlier 
posts; sorry).
>                Speaking as someone who works at a company dedicated to 
helping people deal
>                with interoperability problems, I have to question the 
wisdom of allowing
>                but ignoring multiple instances of these headers. 
Presumably a SOAP node
>                would only inject an additional duplicate header to 
achieve a desired
>                effect. To ensure that effect, the processor would have 
to check to see
>                whether the same header already existed in a message. If 
it did, the
>                processor would presumably either raise an exception or 
put it's header in
>                *before* the present header in order to trump it. There 
would be little
>                reason to put it in after the existing header, since it 
would just be
>                ignored.
>                This raises two questions in my mind. First, what are the 
>                implications? Will this open to WSA to attacks based on 
shifting relative
>                position of a header and require the use of XPath 
expressions in signatures
>                that explicitly specify position relative to soap:Header? 
If multiple
>                instances were disallowed, this issue would go away as 
injecting a duplicate
>                header would invalidate the message.
>                Second, how does all this work relative to headers 
targeted at different
>                actors/roles (are those allowed with WSA?)?
>                While I can see applying the mustIgnore rule to content 
you don't know
>                about, it seems kind of strange to apply it to duplicate 
elements in a given
>                spec. If SOAP allowed multiple soap:Header/soap:Body 
elements in any order,
>                with only the first of each in document order having 
meaning help or hinder
>                interoperability? What about understandability?
>                Thanks,
>                Tim-
>                > -----Original Message-----
>                > From: public-ws-addressing-request@w3.org
>                > [mailto:public-ws-addressing-request@w3.org] On Behalf 
>                > paul.downey@bt.com
>                > Sent: Wednesday, January 12, 2005 11:38 AM
>                > To: noah_mendelsohn@us.ibm.com
>                > Cc: public-ws-addressing@w3.org
>                > Subject: RE: i009 - mustIgnore rule for multiple To, 
ReplyTo, etc.
>                >
>                >
>                > Noah,
>                >
>                > Thanks for your help, in particular the quotation from 
>                > SOAP 1.2 Rec S2.6[1]. I'm assuming that a similar 
>                > model also applies to SOAP 1.1, though i couldn't find 
>                > explicitly stated in the note or the WS-I Basic 
Profile. As
>                > i'm sure you are aware, we are chartered to provide 
>                > for both SOAP 1.1 and 1.2 and I believe it is desirable 
>                > have the same mustIgnore rule for multiple EPRs applied 
>                > both bindings.
>                >
>                > > I'm not recommending one approach or another for 
>                > and friends,
>                > > but just pointing out that the SOAP recommendation 
>                > the option:
>                > > if you want to say in the specification for some SOAP 
header block:
>                > > "all occurrences of blocks with this QName must be 
processed in
>                > > document order", the SOAP Rec. says you can do that.
>                >
>                > That sounds good to me, assuming SOAP 1.1 has the same
>                > processing model.
>                >
>                > > Now, whether most of the widely
>                > > deployed implementations of SOAP make it easy to 
>                > such control
>                > > is a different question.
>                >
>                > Given we're writing a specification I would like to 
think we
>                > can follow correctness here and specify a significance 
to the
>                > order for repeated headers in the wsa namespace.
>                >
>                > >From a brief look at a couple of SOAP APIs taken at 
random it seems
>                > that you can usually iterate through the SOAP headers 
>                > order, though some tools which provide an application
>                > binding, generating code for headers directly described 
>                > WSDL will have difficulties.
>                > Then again such an approach at implementing wsa will
>                > encounter many other difficulties. Maybe this isn't 
such an
>                > issue in practice after all.
>                >
>                > My remaining concern regards a use-case Don Box 
outlined at
>                > our Redmond F2F in which other non-wsa components in a 
>                > processing pipeline may trigger off wsa headers, such 
as EPR
>                > parameters and properties.
>                > Such side-effects could be oblivious to our mustIgnore 
>                > if they encountered a repeated item, but then they 
would have
>                > to consider other items being repeated anyway - i don't 
>                > this as an issue.
>                >
>                > So I'm happy to rewrite the Option#3 proposal more 
>                > to state 'subsequent unexpected wsa:Address, 
>                > wsa:ReplyTo, wsa:FaultTo items must be ignored", 
>                > there's no strong disagreement from the WG on this 
>                >
>                > Paul
>                >
>                > [1] http://www.w3.org/TR/soap12-part1/#procsoapmsgs
>                >
>                >

Tom Rutt                 email: tom@coastin.com; trutt@us.fujitsu.com
Tel: +1 732 801 5744          Fax: +1 732 774 5133
Received on Thursday, 13 January 2005 01:55:54 UTC

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