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RE: First cut policy write up

From: Christopher B Ferris <chrisfer@us.ibm.com>
Date: Mon, 4 Dec 2006 15:24:34 -0500
To: "Gilbert Pilz" <Gilbert.Pilz@bea.com>
Cc: "David Illsley" <david.illsley@uk.ibm.com>, public-ws-addressing@w3.org, public-ws-addressing-request@w3.org, "Yalcinalp, Umit" <umit.yalcinalp@sap.com>
Message-ID: <OF2EE8BCB1.4AC84FA8-ON8525723A.006CE6AF-8525723A.00701C49@us.ibm.com>
I continue to be fascinated with this thread.

> As I recall, we decided that "UsingAddressing" always has one meaning 
which
> is that WS-Addr is "supported".

If this is the case, and that when in conjunction with 
wsdl:required='true' that it effectively changes the
semantic to that of the 11th commandment: "Thou shalt use WS-Addressing", 
then I guess I am confused,
because wsa:UsingAddressing no longer has the semantic of "WS-Addressing 
is supported" except implicitly.
(If the endpoint is admonishing its prospective consumers that they MUST 
use WS-Addressing, lest they
suffer the Wrath of Khan, or the WS-Overlords, or whomever dishes out 
wrath in the context of WS-*dom,
then that admonishment obviously implies that WS-Addressing is supported 
at that endpoint, or else they would not
have written that commandment into their WSDL tablet in the first place.)
.
The semantic of wsdl:required='true' is that it means that the consumer of 
the WSDL MUST
understand that EXTENSION in order that they be able to effectively use 
the WSDL description [1]. WSDL2.0
basically has the same semanic. wsdl20:required='true' effectively means 
that the extension may change the
semantic of the parent WSDL element in a manner in which if not 
understood, would prevent the client
from correctly interacting with the endpoint described.

So, in both cases, what the semantic of wsdl:required='true' adds to a 
given extension is that you MUST
understand that extension's semantic. If wsa:UsingAddressing means 
"WS-Addressing is supported", then
the mere presence of wsdl:required='true' cannot change that semantic into 
"Thou shalt use WS-Addressing".
wsa:UsingAddressing still means "WS-Addressing is supported".

If you want to convey a requirement that WS-Addressing MUST be used, then 
you need an extension that
says that,unambiguously in its semantic, absent the presenceor absenceof 
"wsdl:required='true'.

If you want the semantic that WS-Addressing is supported, but not required 
(e.g. optional) then use wsdl:required='false'
(the default in both cases IIRC) as a means of providing the consumer of 
the WSDL to choose whether they
want to "understand" the semantic of the wsa:UsingAddressing WSDL 
extension (of course, I would strongly
suggest renaming the extension to something a little more descriptive of 
the semantic carried: e.g. wsa:UseAddressing).

If the semantic of the extension means: "Thou shalt use WS-Addressing", 
then clearly, it can be used in WS-Policy
with the wsp:Optional='true' to indicate that there are two policy 
alternatives available to the consumer: one with,
and one without the admonition that "Thou shalt use WS-Addressing".

IMO, wsa:UsingAddressing is broken if its current semantic is 
"WS-Addressing supported" because you
can't change its semantic with wsdl:required='true'since 
wsdl:required='true' isn't intended to CHANGE the semantic
of the extension, but merely to signal to the WSDL processor that it MUST 
understand the extension's semantic.

[1] http://www.w3.org/TR/wsdl#_language
[2] http://www.w3.org/TR/wsdl20/#language-extensibility

Cheers,

Christopher Ferris
STSM, Software Group Standards Strategy
email: chrisfer@us.ibm.com
blog: http://www.ibm.com/developerworks/blogs/page/chrisferris
phone: +1 508 377 9295

public-ws-addressing-request@w3.org wrote on 12/04/2006 02:15:07 PM:

> David's understanding of the semantics of the wsaw:UsingAddressing 
policy
> assertion is in line with my intentions in describing it and (I hope) in
> line with what the group decided on the 11/27 concall.
> 
> As I recall, we decided that "UsingAddressing" always has one meaning 
which
> is that WS-Addr is "supported". When used as a WSDL extension in 
conjunction
> with 'wsdl:required="true"' it means that WS-Addr is required. 
Unfortunately
> there doesn't seem to be a way of both keeping the semantics of
> "UsingAddressing" constant across its use as a WSDL extension and a 
policy
> assertion *and* allowing the WS-Policy variation to express that the use 
of
> WS-Addr is required. I thought we had discussed this and agreed that we
> would have to live with it. If you really need to express the fact that
> WS-Addr is required for an endpoint you will have to use
> wsaw:UsingAddressing as a WSDL extension and mark it with
> 'wsdl:required="true"'.
> 
> As for nested policy assertions, again, I thought we had discussed this 
and
> decided that they were too complicated. I now think we were a bit 
premature
> in that decision and I agree that nested policy assertions work best for
> expressing the relationship between the broad "UsingAddressing" 
assertion
> and the narrower "AnonymousReponses" and "NonAnonymousResponse".
> 
> - gp
> 
> "too forward and one back
>  blind fingers groping for the right track"
> 
> 
> > -----Original Message-----
> > From: David Illsley [mailto:david.illsley@uk.ibm.com] 
> > Sent: Monday, December 04, 2006 4:40 AM
> > To: Yalcinalp, Umit
> > Cc: Gilbert Pilz; public-ws-addressing@w3.org
> > Subject: RE: First cut policy write up
> > 
> > Comments below.
> > 
> > public-ws-addressing-request@w3.org wrote on 12/01/2006 10:34:05 PM:
> > 
> > > > I spent a while yesterday going over this proposal with 
> > Katy, Paco, 
> > > > and our WS-Policy development team and we have a couple 
> > of concerns.
> > > > 
> > > > 1. There is no way to mandate addressing in this proposal i.e. In 
> > > > normal form (once the wsp:Optionals etc have been expanded) the 
> > > > presence of wsaw:UsingAddressing only indicates addressing is 
> > > > supported.
> > > > We need a way
> > > > to say addressing is required. I don't have a proposal 
> > yet to deal 
> > > > with this.
> > > > 
> > > 
> > > I am really not following this point. Could you clarify? 
> > > 
> > > If you do not use wsp:optional and use the standard attachment 
> > > mechanisms, why wouldn't WS-Addressing be NOT required.
> > > 
> > > IF there is no alternative in the policy, the intersection 
> > algorithm 
> > > and thus the client will treat WS-Addressing assertion as 
> > an addition 
> > > that it needs to understood and thus make behavior required.
> > > 
> > 
> > I agree that in those circumstances, the UsingAddressing 
> > assertion would be required for the client.
> > However, the example states:
> > > > <wsp:Policy>
> > > >   <wsaw:UsingAddressing>
> > > > </wsp:Policy>
> > > > This policy indicates that the subject supports the use of
> > WS-Addressing. 
> > 
> > It explicitly does not say that inclusion of UsingAddressing in an 
> > alternative mandates the use of WS-Addressing, merely that it is 
> > supported, hence the concern.
> > 
> > David
> > 
Received on Monday, 4 December 2006 20:25:23 GMT

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