W3C home > Mailing lists > Public > public-ws-addressing@w3.org > August 2006

Re: [ws-rx] Re: Comment on WSDL spec: use of Anonymous Element

From: Alastair Green <alastair.green@choreology.com>
Date: Tue, 08 Aug 2006 12:06:32 +0100
Message-ID: <44D87038.5000102@choreology.com>
To: ws-rx@lists.oasis-open.org
CC: public-ws-addressing@w3.org
Doug, Paul --

I'm going to try to address both your comments. if I can summarize 
Paul's it was: what's the big deal about [reply endpoint] when 
MakeConnection is "one-way"?.

Given RX timescales you may want to treat these remarks as "early public 
review".

* * *

Doug's message 1 is an application-level set-up call which establishes 
common understanding of the UUID. This type of message is exemplified by 
that shown in the CD example Step 1, unless I have completely misunderstood.

In that example, a subscriber, who cannot listen, sends a subscribe 
message to a publisher, saying something like "subscribe me for topics 
A, B, C. The identity of this subscription request is UUID X". 
Thereafter, the publisher knows that X equals "subscription for topics 
A, B, C".

*Assertion 1 *(please correct me if I am wrong): The format, content etc 
of this type of message (and its manner of transmission) are entirely 
application-specific. It may or may not require an acknowledgement. It 
could be sent by carrier pigeon, or by fax. The subscribe message, if 
sent as SOAP-with-Addressing, might receive a reply, or might not 
receive a reply, and if it did, it might receive it anon or addressable. 
There are no RM rules that apply to this message. There are only 
application rules. It cannot do its job usefully unless it passes the 
UUID: that is all we can say.

*Assertion 2*. At present there is an RM rule which says: "the mutually 
understood UUID must be reflected in the [destination endpoint] 
according to an RM URI scheme". There are no RM rules to say whether the 
connection UUID, /during the course of establishing mutual 
understanding/, travels alone, embedded in a URI, in a body element or a 
header element. These are all matters of bilateral agreement at an app 
level between (in this case) the consumer/subscriber and the 
producer/publisher.

[The example is potentially a bit misleading in this respect.

The use of the full "anon-URI?id={uuid}" value in the <targetEPR/>, and 
the use of the element name "targetEPR" make one think "addressing", 
when one would be better off thinking "subscription identity" (at an app 
level). The example set-up message would work perfectly well if it read:

<S:Body>
    <!-- subscription details --> 
    <SubscriptionIdentity>{uuid}</SubscriptionIdentity>
</S:Body>

Btw, given that the use of MakeConnection requires a prior understanding 
between two parties of the connection identity, there seems no reason 
why {uuid} has to be a UUID. It does need to be bilaterally unambiguous.]

* * *

Message 2 is MakeConnection. If the subscriber sends a MakeConnection, 
specifying UUID X, then the publisher knows it is dealing with traffic 
relating to subscription X, i.e. for topics A, B and C. At an 
application level, we assume that the contract thereafter is: start 
reliably communicating a stream of messages, relating to topics A, B and 
C, therefore implying sequence creation etc, until something causes the 
stream to close.

So the subscriber will repeatedly send MakeConnection, citing the UUID 
X, read the HTTP response, and handle the response as if it were an 
inbound RM/RM-app message.

*The exchange that RM defines (rather than illustrates) is the 
MakeConnection, back-call-on-the-connection one. It's this exchange that 
I am discussing. MakeConnection is the message affected by the WSAW 
anon=required discussion, as I see it.
*
[While it is probably helpful for diagnostic reasons to repeat the UUID 
back to the sender of MakeConnection in the [destination endpoint], it 
is actually redundant, as the HTTP Response is automatically and 
uniquely correlated with the HTTP Request. This might lead one to the 
conclusion that the simple solution would have been: send UUID on 
MakeConnection, and then respond to it on the anonymous back-channel 
without reflection of UUID in any form However, this would reduce the 
symmetry with the Sequence identified use of MakeConnection, see 
comments later]

* * *

There are two modes in which this exchange can work (reflecting the 
joint proposal, as I understand it):

a) Send response as part of a sequence that already exists
b) Use response to create a new sequence, etc

This is relevant to answering Paul F's question, relating to the 
significance of ReplyTo.

If there is a sequence, then the sequence Identifier is a correlation 
synonym for the UUID. The reply message may be sent on the back-channel; 
it must carry the wsrm:Identifier (as a separate header element), it 
need not carry the UUID.

If there is no sequence, then the reply message must carry or imply the 
UUID. (I'm going to assume that carrying the UUID is better than 
implying it.) The question is how?

Looking at these two cases, it is striking that both

a) require a response on the back-channel,
b) need to carry an identifier (one of the sequence, one of the 
"connection"/"session")

Doug's comment that there is no wsa:ReplyTo on the MakeConnection, that 
it is "one way", is relevant here. In fact there is no such thing (in 
the XML infoset) as a non-existent [reply endpoint]. /If wsa:ReplyTo is 
absent, then it is inferred to be the anon-URI/. The only way you can 
stop that inference is to set the [reply endpoint] to none or to a "real 
address". I don't think you want to do either of those things, in this 
context.

With these points in mind, I think it is worth looking again at my 
previous postings.

The orthodox way of saying "respond on the back-channel" is setting 
[reply endpoint] to anon. This can be done explicitly or by inference 
from absence.

I think there has to be a good reason to invent a new way of expressing 
this semantic. Doing so has repercussions (see the original starting 
point of this thread, re WSA W anon/required). The (very valuable) use 
case of MakeConnection does not require an alternate mechnanism for 
stating the back channel semantic.

We can illustrate all of this by placing three examples side by side:

* * *

1. Example using sequence Identifier: MakeConnection and reply [as per 
CD 04]
2. Example using hypothetical connection identifier: MakeConnection and 
reply [as it could be, simplified]
3. Example using current Address [as per CD 04]

1a. Example using sequence Identifier: *MakeConnection

*<S:Envelope xmlns:S="http://www.w3.org/2003/05/soap-envelope"
            xmlns:wsrm="http://docs.oasis-open.org/ws-rx/wsrm/200608"
            xmlns:wsa="http://www.w3.org/2005/08/addressing">
    <S:Header>
        
<wsa:MessageID>http://example.org/subscriptionService/guid/61e0654e-5ce8-477b-bb9d-34f05cdcbc9e</wsa:MessageID>
        
<wsa:Action>http://docs.oasis-open.org/wsrx/wsrm/200608/MakeConnection</wsa:Action>
        <wsa:To>http://example.org/subscriptionService</wsa:To>
/<!-- absent wsa:ReplyTo is equivalent to:   
/        <wsa:ReplyTo>
            
<wsa:Address>http://docs.oasis-open.org/wsrx/wsrm/200608/anonymous</wsa:Address>
        </wsa:ReplyTo>
/-->
/    </S:Header>
    <S:Body>
        <wsrm:MakeConnection>           
*            
<wsrm:Identifier>http://Business456.com/SubscribeTopics/Sequence/7456-3278</wsrm:Identifier>
*        </wsrm:MakeConnection>
    </S:Body>
</S:Envelope>

1b. Example using sequence Identifier: *reply to MakeConnection*

<S:Envelope xmlns:S="http://www.w3.org/2003/05/soap-envelope"
            xmlns:wsrm="http://docs.oasis-open.org/ws-rx/wsrm/200608"
            xmlns:wsa="http://www.w3.org/2005/08/addressing">
    <S:Header>
        
<wsa:MessageID>http://example.org/subscriptionService/guid/71e0654e-5ce8-477b-bb9d-34f05cfcbc9e</wsa:MessageID>
        
<wsa:RelatesTo>http://example.org/subscriptionService/guid/61e0654e-5ce8-477b-bb9d-34f05cdcbc9e</wsa:RelatesTo>
        
<wsa:ReplyTo><wsa:Address>http://example.org/subscriptionService</wsa:Address></wsa:ReplyTo>
        
<wsa:Action>http://example.com/subscriptionService/publish</wsa:Action>
        <wsrm:Sequence>
*            
<wsrm:Identifier>**http://Business456.com/SubscribeTopics/Sequence/7456-3278**</wsrm:Identifier>
*            <wsrm:MessageNumber>1</wsrm:MessageNumber>
        </wsrm:Sequence>
    </S:Header>
    <S:Body>
        <!-- Publication re A, B or C -->
    </S:Body>
</S:Envelope>

2a. Example using hypothetical connection identifier:* MakeConnection*

<S:Envelope xmlns:S="http://www.w3.org/2003/05/soap-envelope"
            xmlns:wsrm="http://docs.oasis-open.org/ws-rx/wsrm/200608"
            xmlns:wsa="http://www.w3.org/2005/08/addressing">
    <S:Header>
        
<wsa:MessageID>http://example.org/subscriptionService/guid/61e0654e-5ce8-477b-bb9d-34f05cdcbc9e</wsa:MessageID>
        
<wsa:Action>http://docs.oasis-open.org/wsrx/wsrm/200608/MakeConnection</wsa:Action>
        <wsa:To>http://example.org/subscriptionService</wsa:To>
/<!-- absent wsa:ReplyTo is equivalent to:   
/        <wsa:ReplyTo>
            
<wsa:Address>http://docs.oasis-open.org/wsrx/wsrm/200608/anonymous</wsa:Address>
        </wsa:ReplyTo>
/-->
/    </S:Header>
    <S:Body>
        <wsrm:MakeConnection>           
*            
<wsrm:ConnectionIdentifier>http://Business456.com/**SubscribeTopics/Stream/7457**</wsrm:ConnectionIdentifier>
*        </wsrm:MakeConnection>
    </S:Body>
</S:Envelope>

2b. Example using hypothetical connection identifier: *reply to 
MakeConnection (CreateSequence)*

<S:Envelope xmlns:S="http://www.w3.org/2003/05/soap-envelope"
            xmlns:wsrm="http://docs.oasis-open.org/ws-rx/wsrm/200608"
            xmlns:wsa="http://www.w3.org/2005/08/addressing">
    <S:Header>
        
<wsa:MessageID>http://example.org/subscriptionService/guid/71e0654e-5ce8-477b-bb9d-34f05cfcbc9e</wsa:MessageID>
        
<wsa:RelatesTo>http://example.org/subscriptionService/guid/61e0654e-5ce8-477b-bb9d-34f05cdcbc9e</wsa:RelatesTo>
        
<wsa:Action>http://docs.oasis-open-org/wsrx/wsrm/200608/CreateSequence</wsa:Action>
        <wsa:ReplyTo>http://example.org/subscriptionService</wsa:ReplyTo>
*        <wsrm:ConnectionIdentifier>
            http://Business456.com/**SubscribeTopics/Stream/7457
        **</wsrm:ConnectionIdentifier>*         
    </S:Header>
    <S:Body>
        <wsrm:CreateSequence>
            <wsrm:AcksTo>
                
<wsa:Address>http://example.org/subscriptionService</wsa:Address>
            </wsrm:AcksTo>
        </wsrm:CreateSequence>
    </S:Body>
</S:Envelope>

3a. Example using wsrm:Address:* MakeConnection*

<S:Envelope xmlns:S="http://www.w3.org/2003/05/soap-envelope"
            xmlns:wsrm="http://docs.oasis-open.org/ws-rx/wsrm/200608"
            xmlns:wsa="http://www.w3.org/2005/08/addressing">
    <S:Header>
        
<wsa:MessageID>http://example.org/subscriptionService/guid/61e0654e-5ce8-477b-bb9d-34f05cdcbc9e</wsa:MessageID>
        
<wsa:Action>http://docs.oasis-open.org/wsrx/wsrm/200608/MakeConnection</wsa:Action>
        <wsa:To>http://example.org/subscriptionService</wsa:To>
/<!-- absent wsa:ReplyTo is equivalent to:   
/        <wsa:ReplyTo>
            
<wsa:Address>http://docs.oasis-open.org/wsrx/wsrm/200608/anonymous</wsa:Address>
        </wsa:ReplyTo>
/-->
/    </S:Header>
    <S:Body>
        <wsrm:MakeConnection>           
*            <wsrm:Address>
                
**http://docs.oasis-open.org/wsrx/wsrm/200608/anonymous?id=550e8400-e29b-11d4-a716-446655440000**
            </wsrm:Address>
*         </wsrm:MakeConnection>
    </S:Body>
</S:Envelope>

3b. Example using wsrm:Address: *reply to MakeConnection (CreateSequence)*

<S:Envelope xmlns:S="http://www.w3.org/2003/05/soap-envelope"
            xmlns:wsrm="http://docs.oasis-open.org/ws-rx/wsrm/200608"
            xmlns:wsa="http://www.w3.org/2005/08/addressing">
    <S:Header>
        
<wsa:MessageID>http://example.org/subscriptionService/guid/71e0654e-5ce8-477b-bb9d-34f05cfcbc9e</wsa:MessageID>
        
<wsa:RelatesTo>http://example.org/subscriptionService/guid/61e0654e-5ce8-477b-bb9d-34f05cdcbc9e</wsa:RelatesTo>
        
<wsa:Action>http://docs.oasis-open-org/wsrx/wsrm/200608/CreateSequence</wsa:Action>
        *<wsa:To>

*/<!-- I believe this is WS-A illegal: reply To must equal request 
ReplyTo/Address. -->/*          
**
            
http://docs.oasis-open.org/wsrx/wsrm/200608/anonymous?id=550e8400-e29b-11d4-a716-446655440000
        </wsa:To>
**        *<wsa:ReplyTo>http://example.org/subscriptionService</wsa:ReplyTo>
**    </S:Header>
    <S:Body>
        <wsrm:CreateSequence>
            <wsrm:AcksTo>
                
<wsa:Address>http://example.org/subscriptionService</wsa:Address>
            </wsrm:AcksTo>
        </wsrm:CreateSequence>
    </S:Body>
</S:Envelope>

Yours,

Alastair

Doug Davis wrote:
>
> Alastair,
>   I think you're mixing up the messages a bit.  There are two messages
> at play:
> 1 - the message containing the EPR to send subsequent messages to.  
>     In some cases this message will have the EPR in its wsa:ReplyTo
>     header, but it could also be placed someplace else depending
>     on its use.  And it is this EPR that needs to be tagged as the
>     polling one (ie. it has the RM anon URI).
>     This message will contain application specific data in the Body
>     so your suggestion of placing some UUID in there will not work.
>     This gets back to the necessity to keep all info about where to
>     send messages encapsulated into whatever EPR we want to be tagged
>     as the polling one.
>
> 2 - the MakeConnection message.
>     This message does not have a wsa:ReplyTo, its a one-way.  This
>     message does contain a Body which is the correlation info used
>     by the receiver of this message to find an appropriate message
>     to send back.  So, basically the stuff in the Body must match
>     the EPR from message 1.  And given that in some cases the only
>     thing remaining from the EPR in message 1 is the serialized
>     version of it, we must be able to find messages based solely
>     on what's in the outgoing message itself.  Which means the
>     wsa:To field.  Again, ref-p's are bad for this purpose. :-)
>
> HTH
>
> thanks
> -Doug
>
>
>
> Alastair Green <alastair.green@choreology.com> wrote on 08/07/2006 
> 02:02:55 PM:
>
> > Doug,
> >
> > I think I'm connecting, if you'll pardon the pun.
> >
> > 1. As I read WS-A, the [destination endpoint][address] must be set
> > to [reply endpoint][address] for a reply.
> >
> > 2. If [reply endpoint] is omitted (as per the CD example), then
> > [reply endpoint] = anon, by default.
> >
> > 3. If [destination endpoint] = "anon-URI?id={uuid}", then
> > [destination endpoint] <> [reply endpoint][address] (which was
> > simple, unornamented anon-URI), which contradicts premise 1.
> >
> > Does that make sense? If so, then I think you would need to set
> > [reply endpoint] to none, explicitly, to avoid that clash (given
> > RM's current approach). But this causes
> >
> > 4. The WS-A processor that sent MakeConnection to get very confused.
> > It wasn't expecting anything but an HTTP 200 series by way of a
> > response, but is about to get a full-scale SOAP message bounding back.
> >
> > +++
> >
> > Further thoughts, which continue, in my mind, to question the
> > current RM approach, but which may ease the WSA W problem.
> >
> > a) You could have defined an extension element in the [reply
> > endpoint] for the UUID.
> >
> > b) Or, you could have chosen to send the UUID in the body element.
> >
> > c) In either case, this could team up with setting [reply endpoint] 
> to anon.
> >
> > d) As in 3. above, you shouldn't then set response [destination
> > endpoint] to anon?id={uuid}.
> >
> > e) So, you need to set [reply endpoint] to anon, and set
> > [destination endpoint][address] to anon.
> >
> > f) which begs the question, where does the UUID go?
> >
> > g)  If you passed an extension element UUID, or a UUID in the body
> > element, and then passed it back as an extension element in the anon
> > EPR that should be OK, because you have followed the rules for reply
> > formulation with respect to the [destination endpoint][address]
> > /[reference parameters]. The fact you have chosen to put an
> > extension element in the response is WS-A 3.3/3.4 legal, as I read
> > it. That's a higher-layer behaviour that does not contradict WS-A
> > base behaviour, which is constrained.
> >
> > +++
> >
> > Why is g) not viable in your view? The processors that need to
> > understand the body/extension UUID element are the RM senders and
> > responders (not the WS-A processors, which passively pass on the
> > UUID to the RM receiver of MakeConnection, and pass on the extension
> > element to the RM receiver of the response).
> >
> > In other words, the awareness of RM-ness that is demanded in
> > formulating MakeConnection, and in replying to it, resides in the
> > same place, and at the same level, as in the current (CD) solution.
> >
> > The difference being: that the MakeConnection is now a regular
> > [reply endpoint] = anon. At which point special WSAW rules are not 
> needed.
> >
> > I don't see any lesser or greater problem with intermediaries,
> > onward transmission etc than would apply with the current solution,
> > if that is a concern. On this point, I think I may be missing
> > something, or misunderstanding your area of concern?
> >
> > So, to summarize:
> >
> > 1. asimple-non out, special, ornamented-anon back is a problem.
> > 2. none out, anon back is a problem.
> > 3. extension element UUID out, extension element UUID back, is no
> > different, in layer terms, than body UUID out, ornamented address
> > back, i.e. is not a problem.
> > 4. anon out means no problem with anon = required.
> >
> >
> > * * *
> >
> > My last point was indeed completely beside the point of your issue :
> > -) -- it is an independent issue about WSAW, and a limitation that
> > the proposed syntax seems to impose by applying the flag across all
> > "response endpoints".
> >
> > Alastair
> >
> > Doug Davis wrote:
> >
> > Alastair,
> >   We did consider adding some extra metadata to the EPR (outside of
> > the wsa:Address and ref-p's), but there's a problem - this metadata
> > is not copied over into the response message - just the wsa:Address
> > and ref-p's are.  This means that any data placed elsewhere in the
> > EPR is lost once the message is serialized.  So unless we assume the
> > impl can hold on to the original EPR for the entire message path
> > (which we can't in distributed systems), the identity part must be
> > in either the address or ref-p's.  And, as you said, ref-p's aren't
> > good for this.
> >
> >   What's interesting about your anon?unique-id example is that that
> > solution might work very nicely (we talked about this in the past) -
> > but as you said it would require WSA to say anon URIs 'start
> > with...' - and WSA is closed :-(
> >
> >   I got a bit lost on your last point - it almost sounded like a
> > complaint about the current WSA WSDL spec instead of my issue -  or
> > did I not follow it?
> >
> >   I noticed that on the agenda for tomorrow's WSA call (I think its
> > tomorrow) is a CR issue that mentioned how this wording in the WSDL
> > spec prevents the use of "none".  I can't help but think that both
> > issues (mine and the other CR issue) would be solved nicely if the
> > wording were turned around a bit and said something about how this
> > flag indicates whether or not the endpoint supports addressable
> > endpoints in the response EPRs.  Not sure of the exact wording, but
> > if instead of taking about specific URIs (like anon and none) it
> > talked about whether the endpoint supported the notion of creating
> > it own connections to the EPR then it wouldn't need to get into the
> > business of listing all of the URIs that are valid.  And I think it
> > would relay the exact same information.
> >
> > thanks
> > -Doug
> >
> >
>
> >
> > Alastair Green <alastair.green@choreology.com>
> > 08/04/2006 10:57 AM
> >
> > To
> >
> > Doug Davis/Raleigh/IBM@IBMUS
> >
> > cc
> >
> > public-ws-addressing@w3.org, public-ws-addressing-request@w3.org,
> > ws-rx@lists.oasis-open.org, abbieb@nortel.com, aclark@novell.com,
> > akira.tanaka.pr@hitachi.com, aleyfer@actional.com, 
> anash@reactivity.com,
> > andreas.bjarlestam@ericsson.com, anil.edakkunni@soa.com, 
> anil.john@jhuapl.edu
> > , Anish.Karmarkar@oracle.com, Anthony Nadalin/Austin/IBM@IBMUS,
> > asakala@iona.com, ash@rainingdata.com, ashok.malhotra@oracle.com,
> > asirveda@microsoft.com, atarashi@sv.nec-labs.com, atmanes@gmail.com,
> > audet@nortel.com, barreto@adobe.com, bhakti.mehta@sun.com, blake.
> > dournaee@intel.com, bob.freund@hitachisoftware.com, 
> bob.sunday@pwgsc.gc.ca,
> > b.eckenfels@seeburger.de, carolina.canales@ericsson.com, 
> chamikara@wso2.com,
> > chappell@sonicsoftware.com, Charles Levay/Raleigh/IBM@IBMUS,
> > chouthri@sv.nec-labs.com, Christopher B Ferris/Waltham/IBM@IBMUS,
> > Christopher.Kurt@microsoft.com, chris.hipson@bt.com, "'von Riegen, 
> Claus'"
> > <claus.von.riegen@sap.com>, coevans@microsoft.com, 
> cunningham_david@bah.com,
> > dan@actional.com, "'Burdett, David'" <david.burdett@sap.com>,
> > dconnelly@openapplications.org, Diane Jordan/Raleigh/IBM@IBMUS,
> > dkmin@konkuk.ac.kr, dleshc@tibco.com, dmoberg@us.axway.com, 
> dnickull@adobe.com
> > , "'David Orchard'" <dorchard@bea.com>, doug.bunting@sun.com,
> > eisaku.nishiyama.dd@hitachi.com, email@cbvenkat.net, 
> eoghan.glynn@iona.com,
> > Eric.Newcomer@iona.com, eric.rajkovic@oracle.com, eric.
> > wells@hitachisoftware.com, ganga.sah@oracle.com, gatfora@uk.ibm.com,
> > gboschi@sonicsoftware.com, gdaniels@sonicsoftware.com, "'Gilbert Pilz'"
> > <Gilbert.Pilz@bea.com>, girish.juneja@intel.com, 
> gregcarp@microsoft.com,
> > greg.pavlik@oracle.com, hbenmalek@us.fujitsu.com, 
> heiko.braun@jboss.com,
> > ian.c.jones@bt.com, ian_robinson@uk.ibm.com, james.speer@capgemini.com,
> > jamie.clark@oasis-open.org, jdurand@us.fujitsu.com, jeff.
> > mischkinsky@oracle.com, jekanaya@cs.indiana.edu, 
> Jiri.Tejkl@systinet.com,
> > jjchoe@tmax.co.kr, jkchoi@methodi.com, jmarsh@microsoft.com, joeri.
> > van_cleynenbreugel@alcatel.be, john.gotze@oasis-open.org, 
> john.kemp@nokia.com
> > , joseph.2.waller@bt.com, junghc@nca.or.kr, jypyon@nca.or.kr, k-
> > seki@da.jp.nec.com, kcyee@cecid.hku.hk, kiwasa@jp.fujitsu.com,
> > lburch@novell.com, lily.liu@webmethods.com, "'Lei Jin'" <ljin@bea.com>,
> > machi@nca.or.kr, "'Mark Little'" <mark.little@jboss.com>,
> > "'Schenecker, Mark'" <mark.schenecker@sap.com>, "'de Boer, Martijn'"
> > <martijn.de.boer@sap.com>, "'Raepple, Martin'" 
> <martin.raepple@sap.com>,
> > mary.mcrae@oasis-open.org, matsuki.yoshino.pw@hitachi.com, 
> mckierna@uk.ibm.com
> > , mgoodner@microsoft.com, mhb@itst.dk, "'Bechauf, Michael'"
> > <michael.bechauf@sap.com>, mike.grogan@sun.com, millwood@uk.ibm.com,
> > mlovett@uk.ibm.com, mlyons@layer7tech.com, mschenecker@e2open.com,
> > mwang@tibco.com, nickr@enosis.com, nilo.mitra@ericsson.com,
> > nobuyuki.yamamoto.vw@hitachi.com, Ondrej.Hrebicek@microsoft.com, 
> paul@wso2.com
> > , pauld@mitre.org, paul.cotton@microsoft.com, paul.knight@nortel.com,
> > peter.furniss@erebor.co.uk, peter_niblett@uk.ibm.com, 
> pete.wenzel@sun.com,
> > prateek.mishra@oracle.com, pyendluri@webmethods.com, Richard
> > Salz/Cambridge/IBM@IBMUS, robin@oasis-open.org, sada@jp.fujitsu.com,
> > "'Patil, Sanjay'" <sanjay.patil@sap.com>, sanka@wso2.com, 
> scayron@acord.org
> > , Scott Hinkelman/Austin/IBM@IBMUS, shengsong.ni@oracle.com,
> > shivajee@tibco.com, srcarter@novell.com, stefanba@microsoft.com,
> > "'Rossmanith, Stefan'" <stefan.rossmanith@sap.com>, "'Winkler, Steve'"
> > <steve.winkler@sap.com>, sumit.gupta@oracle.com, 
> tboubez@layer7tech.com,
> > tejeswar.das@iona.com, thomas.erl@soasystems.com, 
> thomas.t.bui@boeing.com,
> > timothy@drummondgroup.com, toby.considine@unc.edu, tom@coastin.com,
> > "'Yalcinalp, Umit'" <umit.yalcinalp@sap.com>, vfurman@webmethods.com
> > , "'Shipkowitz, Vicki'" <vicki.shipkowitz@sap.com>, 
> vikas@sonoasystems.com
> > , "'Videlov, Vladimir'" <vladimir.videlov@sap.com>, Martin Chapman
> > <martin.chapman@oracle.com>
> >
> > Subject
> >
> > Re: Comment on WSDL spec: use of Anonymous Element
> >
> >
> >
> >
> > Hi Doug,
> >
> > Comments interspersed:
> >
> > Doug Davis wrote:
> >
> > Alastair,
> >  There are a couple of different things at play here. First, sorry
> > about the long cc-list but the wsrx mailing list still doesn't
> > appear to work so I need to include the entire wsrx team manually :-(
> > I thought my mail client was going to expire when I just did "reply 
> all".
> >
> > In a non-anonymous world the wsa:Address field represents both the
> > fact that the destination can access connections and it identifies
> > the party.  And I think that makes sense.  There is no reason to not
> > have a single URI do that (let's not get into the 'identity' issue
> > w.r.t. ref-p's  :-).   So, if we then switch over to the anonymous
> > case, IMO, I don't believe the implementation should need to change
> > w.r.t. the purpose of this URI.
> > Here's what I don't understand. In the non-anon case an EPR (address
> > + stuff) is used to target. In the anon case, so far as I can tell,
> > there is nothing in WS-A to stop the same "full EPR" (address +
> > stuff) being used to target the reply.
> >
> > If one pursues this, what you intuitively want is: callback EPR =
> > {address = anon URI, ref-param[0] = identity}.
> >
> > But ref-params are opaque. Not what you want. (Although I can't see
> > how to stop an app contract, e.g. RM, specifying that we'll use a
> > mutually-known type for a ref-param, and make its presence mandatory
> > for certain messages).
> >
> > Assume that ref-param is not good. Why not add an RM extension
> > element to the EPR? This retains the identity lexeme within the EPR.
> > A WS-A impl should be happy to insert and extract such extension
> > elements, even if it hasn't a clue what they mean.
> >
> > In the simple WS-Addr anon use-case the URI still indicates both
> > things - whether or not (and 'not' in this case) the destination
> > will accept a connection, and it also indicates the identity - sort
> > of.  The identity is implicitly defined by the fact that it is tied
> > to the connection on which the request came in on.  If we did what
> > you're suggesting and add a second header then, IMO, RM would
> > require quite a big change to people's soap processor.  I think WS-
> > Addr did a really good thing by keeping everything people need to
> > know with a single structure - the EPR.  Even with the introduction
> > of the anonymous URI (which could very easily have been introduced
> > in a much less cleaner fashion), most of the SOAP processor doesn't
> > really need to know what the specific value of the wsa:Address
> > element is until it tries to actually send the message over the wire.
> >  So, if we then switch over the MakeConnection use-case, I think RM
> > did the right thing by using the same mechanism WS-Addr did - keep
> > everything within a single EPR.  
> > OK, but I think you may be conflating "a single EPR" with "the
> > address element of a single EPR".
> >
> > This allows for most of the SOAP processor to be totally unaware of
> > the actually transport mechanism until (or close to) the time the
> > message is serialized on the wire.  If there were additional headers
> > to carry this information then existing WS-Addr logic of mapping a
> > wsa:ReplyTo over to a wsa:To + ref-p headers when constructing a
> > response might need to also change.  There's also lots of other use-
> > cases where the logic to handle the RM code isn't on the same
> > machine doing this WS-Addr mapping so if its not aware of RM at all
> > it wouldn't even know to include some special bit on the outgoing
> > message (either in the message or in the soap processor's metadata
> > about the message) to indicate that MakeConnection will be used.  
> > Things are just a whole lot easier if everything is encapsulated in
> > a single EPR, and more specifically in the wsa:Address field.  Which
> > is exactly how WS-Addr anon works today.
> > Hmm, back to the conflation. I can't see anything in the WS-Addr
> > spec that prevents use of ref params, metadata or extensibility
> > elements within an anon EPR.  Here, you want to use the special
> > value of [address], and put an application-defined type/value in the
> > rest of the EPR. That would fit your requirement to "keep it in the 
> EPR".
> >   I don't think loosening the wording makes thing indeterminate - it
> > still requires a URI with the proper semantics, but it allows for
> > the composition of other specifications that may defined their own.
> > And, IMO, as long as they are consistent with WS-Addr's definition
> > of anon, from a WS-Addr perspective, then how they choose to add
> > additional semantics is up to them.
> > I'm not convinced. I think you are layer-violating -- introducing
> > precisely the problem that you are trying to avoid.  
> >
> > At the SOAP processing level this message is full of arcane headers
> > of unknown meaning. At the WS-A processor level, these are
> > commonplace headers with well-defined meanings, which may contain
> > some arcane app ref params and extension elements of unknown meaning.
> >
> > [reply endpoint][address] = anon URI means: "send a response on the
> > back-channel". At the last minute the WS-A processor whacks the
> > arcana (ref-params, metadata and extensibility elements) into the
> > header and whisks them off on the response. Receiving WS-A processor
> > gives the arcana to the app, for which they are meaningful (for
> > routing or correlation or whatever).
> >
> > This works because the WS-A receiver can look at well-known,
> > expected endpoint [reply endpoint] and can find the well-known,
> > expected anon URI -- and need think no further. Anon URI = use back 
> channel.
> >
> > If the URI is different (anon-URI?tum-ti-tum-ti-tum) then the WS-A
> > processor has to assume that it's something special. In fact, it's
> > going to try to address it as a "real address", surely? Only the RM
> > layer knows that "?<string>" is irrelevant to back-channel choice.
> >
> > I can think of three ways of getting around this:
> >
> > 1) Amend WS-Addressing Core to say: the distinguished URI is "any
> > URI which begins with the following distinguished string".
> >
> > 2) Amend WS-Addressing Core to say: the following distinguished
> > metadata element or additional property means: whatever the content
> > of [address], use the back-channel.
> >
> > 3) Put an extension element in the EPR that is routing data at the 
> app level.
> >
> > 1) & 2) involve amending WS-Addressing, which doesn't seem like a 
> great idea.
> >
> > 3) Involves no change to WS-Addressing.
> >
> > If the WSDL says: anon is required, then what is the value inserted
> > on the wire for [reply endpoint][address]? If more definition is
> > required to establish that, then we seem to be losing the low-level,
> > generic capability WS-Addressing has defined. That's what I meant by
> > indeterminacy.
> >
> >
> >  In talking about this with Chris Ferris, he mentioned another
> > alternative... instead of saying "MUST", perhaps the text related to
> > the wsaw:Anon flag could simply say "SHOULD".  This clearly
> > indicates that WS-Addr's anon URI is the URI of choice, but if there
> > are good reasons for using some other one then the processor will
> > allow those as well.
> > Let me raise another point about the WSAW wording. It  talks about
> > "response endpoints" in the plural. Will the required, etc apply to
> > all endpoints which can be responded to, i.e. [from e], [reply e],
> > [fault e], or is it specific to each? It seems to imply the former.
> >
> > If ths is so, then it precludes routing tricks like the following
> > (which is practically useful):
> >
> > [from endpoint] is my address if you need to send me a second (e.g.
> > repeated) response.
> > [reply endpoint] = anon-URI, which is where to send your first
> > response, which we hope gets through.
> >
> > This feature allows retrying protocols to maximize use of HTTP
> > responses, but not be limited by them. I would like to be able to
> > express this as a contractual statement: this endpoint may be anon,
> > this one must not be: from/prohibited, reply/optional. I have a use
> > case in a customer business protocol for exactly this behaviour. I
> > think it's a useful optimization in other contexts.
> >
> > Yrs,
> >
> > Alastair
> >
> > thanks,
> > -Doug
> >
>
> >
> > Alastair Green <alastair.green@choreology.com>
> > Sent by: public-ws-addressing-request@w3.org
> > 08/04/2006 06:59 AM
> >
> > To
> >
> > Doug Davis/Raleigh/IBM@IBMUS
> >
> > cc
> >
> > public-ws-addressing@w3.org, ws-rx@lists.oasis-open.org
> >
> > Subject
> >
> > Re: Comment on WSDL spec: use of Anonymous Element
> >
> >
>
> >
> >
> >
> >
> >
> >
> > Doug,
> >
> > This is probably a dumb question, but aren't you trying to change the
> > wrong spec?
> >
> > In RM you are using a single header property to indicate two things:
> > "we're doing back-channel here, and it's part of a logical connection,
> > identified thus".
> >
> > Why can't you separate the communication of these two semantics, by
> > using two properties:
> >
> > 1) wsa:ReplyTo = anonymous URI
> > 2) wsrm:MakeConnection = connection identity?
> >
> > 2) without 1) would be illegal.
> >
> > In your example posted on the WS-RX list, you state that [reply
> > endpoint] is not set because MakeConnection is a "one-way message". But
> > it's a message that usually/frequently expects a reply (at a WS-A
> > level). Unlike many other applications, a WS-RM MC sender will tolerate
> > an empty response (no SOAP in the HTTP body), but I don't think that
> > stops one viewing this as a utilization of the request-reply pattern
> > implied by use of reply-to.
> >
> > If you loosen the WSAW wording, then surely it becomes indeterminate.
> > What does "required" imply on the wire, thereafter?
> >
> > Alastair
> >
> > Doug Davis wrote:
> > >
> > > To elaborate a little on Bob's note [1], in the WSA WSDL spec, when
> > > talking about the various values for the Anonymous Element it lists:
> > >
> > > "optional": This value indicates that a response endpoint EPR in a
> > > request message MAY contain an anonymous URI as an address.
> > > "required":This value indicates that all response endpoint EPRs in a
> > > request message MUST always use anonymous URI as an address.
> > > If a response endpoint EPR does not contain the anonymous URI as an
> > > address value, then a predefined InvalidAddressingHeader fault 
> defined
> > > in Web Services Addressing 1.0 - SOAP Binding [WS-Addressing SOAP
> > > Binding] MUST be generated.
> > > "prohibited":This value indicates that any response EPRs in a request
> > > message MUST NOT use anonymous URI as an address.
> > > If a response endpoint EPR contains the anonymous URI as an address
> > > value, then a predefined InvalidAddressingHeader fault defined in Web
> > > Services Addressing 1.0 - SOAP Binding [WS-Addressing SOAP Binding]
> > > MUST be generated.
> > >
> > >
> > > The problem comes up when another spec defines their own version of
> > > anonymous - like WS-RM does.  It defines an anon URI which acts 
> almost
> > > exactly like the WSA one in that it means "send it on the transport
> > > specific back-channel".  However, if the wsaw:Anonymous element is 
> set
> > > to "required" then the above text would seem to imply that regardless
> > > of whether or not the RM spec is supported by the endpoint, the 
> client
> > > can never send a wsa:ReplyTo with anything other than WSA's 
> anonymous.
> > >  So the above text precludes another spec from ever extending WSA to
> > > define their own anon URI where from a WSA perspective its 
> equivalent.
> > >  If the text were loosened up a bit to not mention the WSA anon URI
> > > specifically, but rather something more generic like: "... MUST 
> always
> > > use a URI implying the transport specific back-channel" then the use
> > > of the wsaw:Anonymous element would not preclude other specs defining
> > > their own anon URI and not violate the meaning of the wsaw:Anonymous.
> > >
> > > thanks
> > > -Doug
> > >
> > >
> > >
> > > [1]
> > > 
> http://lists.w3.org/Archives/Public/public-ws-addressing/2006Aug/0009.html 
>
> >
> >
Received on Tuesday, 8 August 2006 11:08:04 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Tuesday, 2 June 2009 18:35:14 GMT