RE: WS-Eventing Issue 6425 proposal

Doug,
 
The whole proposal is quite simple and only one sentence: "The event
source shall be addressed by a WS-Addressing 1.0 EPR and the request
message shall be sent to this EPR, as defined in WS-Addressing 1.0 Core
Section 3.1-3.3."

The intention is to prevent subscriber from using ad-hoc method (e.g.
custom soap headers) outside EPR to indicate targeted event source.
Normatively referencing REC version of WS-Addressing can mean too many
things, e.g. core, soap/wsdl, meta information, etc. The concern is:
some implementation may claim normative referencing to WS-Addressing and
WS-Eventing, while using some additional information outside the EPR to
indicate targeted event source. If this happens, interoperability will
become an issue.

We are open to suggestions to refine this sentence. We had a discussion
with Gil and he said he would give it a try.

Thanks,

- Wu Chou.

________________________________

From: Doug Davis [mailto:dug@us.ibm.com] 
Sent: Friday, February 06, 2009 11:30 AM
To: Chou, Wu (Wu)
Cc: Gilbert Pilz; public-ws-resource-access@w3.org;
public-ws-resource-access-request@w3.org
Subject: RE: WS-Eventing Issue 6425 proposal



Hi Wu, 
  thanks for the reply.  Can you elaborate a bit more on why this is
needed?  While I understand what you said in your note, I'm struggling
with why this one specification is special.  By this I mean, other WS
specs don't make this kind of statement.  How the client obtains the
reference to the service is really left as an exercise for reader.
Whether the reference came from WSDL, or from some registry, or whether
its a full EPR or just a URI are all problems that the client just has
to deal with.  And this is true for any interaction between a client and
service.  We've agreed that WS-Eventing will normatively reference (and
use) the REC version of WS-Addressing, so do we really need to say
anything more? 
  I get the sense that there's something deeper behind this that I'm
missing.  Perhaps it would help me understand it better if I turn this
around and ask what would break or cause an interoperability problem by
not having this additional sentence?  Do you have an example of a case
where even after both parties agreed to use the REC version of
WS-Addressing, there were still interop issues?  Does this sentence
imply any new requirements on either party?  For example, does this
require the event source's WSDL to include an embedded EPR in the port? 

thanks
-Doug
______________________________________________________
STSM |  Standards Architect  |  IBM Software Group
(919) 254-6905  |  IBM 444-6905  |  dug@us.ibm.com 



"Chou, Wu (Wu)" <wuchou@avaya.com> 
Sent by: public-ws-resource-access-request@w3.org 

02/06/2009 11:04 AM 

To
Doug Davis/Raleigh/IBM@IBMUS, "Gilbert Pilz" <gilbert.pilz@oracle.com> 
cc
<public-ws-resource-access@w3.org>,
<public-ws-resource-access-request@w3.org> 
Subject
RE: WS-Eventing  Issue 6425 proposal

	




Doug, Gil,   
  
Thanks for your comments. The whole proposal 6425 is to add one
sentence: "The event source is addressed by a WS-Addressing 1.0 EPR and
the request message shall be sent to this EPR, as defined in
WS-Addressing 1.0 Core Section 3.1-3.3." 
  
We feel this more definitive statement  is needed, because there are
multiple versions of WS-Addressing being used and there are multiple
ways to interpret/use event source and EPR in current WS-Eventing. 
  
You can ignore all the rest  in this proposal, i.e. the 2nd part
(background/rationale), because the second part is just some background
information. It is not part of the proposed change to WS-Eventing.   
  
Regards, 
  
- Wu Chou 
  
Wu Chou, IEEE Fellow, Ph.D. | Director |Avaya Labs Research | AVAYA |
233 Mt. Airy Road| Rm. 2D48 | Basking Ridge, NJ 07920 | Voice/Fax:
908-696-5198 / 908-696-5401 | wuchou@avaya.com <mailto:wuchou@avaya.com>




________________________________

From: Doug Davis [mailto:dug@us.ibm.com] 
Sent: Wednesday, February 04, 2009 8:26 PM
To: Chou, Wu (Wu)
Cc: public-ws-resource-access@w3.org;
public-ws-resource-access-request@w3.org
Subject: Re: WS-Eventing Issue 6425 proposal


Wu, 
 I don't understand the purpose behind the first part of your proposal.
I think WS-Eventing is pretty clear that the Subscribe is sent to the
Event Source and that the Event Source's EPR turns into the WSA headers
- per WSA rules.  Could you elaborate on why there is confusion on this?


 On the 2nd part of your proposal... I think what you are proposing, if
I understand it, is mostly fine but out of scope for WS-Eventing.  When
a Subscriber sends a Subscribe() message to an Event Source it had to
get the Event Source's EPR from someplace - perhaps some WSDL.
Regardless of how it got that EPR, it is up to the Event Source to
determine what the EPR looks like.  If it wants to have reference
parameters that have a portType or csta ID then that's fine but its not
really any of WS-Eventing concern how it makes this decision.  But most
importantly, the subscriber should not need to know this or even care.
To it, the EPR is just an opaque bit of XML. 

 Also, within your proposal you talk about using ref-params as a, sort
of, filtering mechanism.  While this is legal because an Event Source
can choose to define what its EPRs look like - I think moving ref-params
from being used for identifications or routing purposes and into the
realm of filtering an event stream is a poor design choice.  This mixing
of concerns is bound to make for a much more complex and fragile system.
The WSA headers (and ref-params) are meant to address the event source
and nothing more. As long as the event source's EPR is an opaque object
then this mixing of concerns (while wrong, IMO) is not something we can
stop since the Event Source is free to decide how its EPRs are made.
However, quoting your proposal: 
The above use cases requires an event subscriber to provide some
additional information, besides the 
service location URI defined in the Event Source WSDL, to associate a
subscription with the targeted 
individual event source (a resource or a port type). 
worries me because when you talk about an event subscriber "providing
additional information" then it sounds like you want the subscriber to
not just use the EPR provided to it by an Event Source, but rather you
want it to modify the ref-params to add this 'additional information'.
At this point the EPR is no longer opaque and the subscriber must now
understand the internal design choices that the Event Source made about
how its EPRs are constructed.  This assumed shared knowledge is not
something WS-Eventing (or other WS specs - like WS-Session) should
promote. 

thanks
-Doug
______________________________________________________
STSM |  Standards Architect  |  IBM Software Group
(919) 254-6905  |  IBM 444-6905  |  dug@us.ibm.com 


"Chou, Wu (Wu)" <wuchou@avaya.com> 
Sent by: public-ws-resource-access-request@w3.org 

02/03/2009 03:28 PM 



To
<public-ws-resource-access@w3.org> 
cc
Subject
WS-Eventing  Issue 6425 proposal


	





 
 
Wu Chou, IEEE Fellow, Ph.D. | Director |Avaya Labs Research | AVAYA |
233 Mt. Airy Road| Rm. 2D48 | Basking Ridge, NJ 07920 | Voice/Fax:
908-696-5198 / 908-696-5401 | wuchou@avaya.com
<blocked::mailto:wuchou@avaya.com>  
[attachment "wse_6425_2.pdf" deleted by Doug Davis/Raleigh/IBM]