RE: WS-Eventing Issue 6425 proposal

Hi Wu,
  So, with this proposal would this message be invalid:
<s:Envelope xmlns:s="...">
 <s:Header/>
 <e:Subscribe xmlns:e=".../ws-eventing">
  <e:Delivery mode=".../broadcast"/>
 </e:Subscribe>
</s:Envelope>

Where someone wanted to use WS-Eventing to have events broadcast rather 
than sent to one particular EPR?  In an environment where this message may 
be sent on an HTTP request flow, there may not be the need for any 
WSAddressing headers.  While I personally want people to always use 
WS-Addressing (I think it should have been part of soap itself ;-),  I'm 
not sure that in a composible archetecture (like Web Services) we should 
have WS-Eventing itself be so prescriptive.  For example, during the F2F 
someone mentioned that they wanted the option of using the member 
submission of WS-Addressing - while I'm not in favor of WS-Eventing 
promoting that spec, I'm not sure we should put something in WS-Eventing 
that would ban it either.  This seems like something that would be better 
suited for a profile.

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
02/10/2009 02:29 PM

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


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 
[attachment "wse_6425_2.pdf" deleted by Doug Davis/Raleigh/IBM]