Re: Comment on WSDL spec: use of Anonymous Element

[Doug Davis <dug@us.ibm.com>]

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 :-(
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. 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.  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.
  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. 
  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.

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