RE: [Bug 6692] New: Remove Mode from the specification

  since its too easy for things to get lost in these long messages, let me 
focus on one particular aspect of this.  Surely the idea of using a proxy 
for sending messages is not WS-Eventing specific.  How do you support 
sending any other asynchronous message (non-NotifyTo messages) thru a 
proxy?  For example, the SubscriptionEnd message.

STSM |  Standards Architect  |  IBM Software Group
(919) 254-6905  |  IBM 444-6905  |
The more I'm around some people, the more I like my dog.

"Chou, Wu (Wu)" <> 
03/31/2009 12:18 AM

Doug Davis/Raleigh/IBM@IBMUS
"Asir Vedamuthu" <>, "Bob Freund" 
<>, "Li, Li (Li)" <>, 
<>, <>, 
RE: [Bug 6692] New: Remove Mode from the specification

Many thanks for your comments. Let's separate the concerns  and focus on 
each thread.
1) Keep Mode attribute of Delivery in WS-E: The use case is to establish 
legitimate critical applications  based on  Mode attribute of Delivery in 
WS-Eventing. It should not remove Mode from the WS-E specs,  because it 
will affect and break the protocol used by existing applications and 
2) EPR usage patterns: Let's definitely find sometime to discuss EPR 
extensions, and I will follow up with you on that. 
My thinking is: EPR can do many things but not everything. In our 
"out-of-band proxy" use case, the NotifyTo EPR is exactly the same for 
both cases, no matter it needs to go through the proxy or not, e.g.  " "  . The out-of-band proxy can be opaque to the 
subscriber, e.g. a between enterprise IT 's  agreement. The event source 
cannot differentiate two different event delivery modes just from the EPR 
in NotifyTo. And this is where the Mode attribute of Delivery in WS-E 
becomes critical.
It is possible to put <ext:Proxy> as part of the NotifyTo EPR. But it is 
not all clear what event source should do to it. EPR alone does not 
provide the declarative semantics to event source  on  how it should treat 
<ext:Proxy>. For example, <ext:Proxy> should not be interpreted as 
reference parameters of the sink, because it is the EPR of the routing 
proxy which is a separate resource entity. 
By the opaque rule recommendation of EPR, event source should copy 
NotifyTo EPR and send the event back. But this will not work here. In 
order to deliver event correctly, the event source must do some "deep" 
semantic analysis of the EPR , and derive from the EPR the semantic action 
that it has to perform - must  deliver  the events  through  <ext:Proxy> 
to the sink. If it cannot do that, it must fault the subscription. This is 
where the Mode attribute of Delivery in WS-E is needed as described in our 
use case.
- Wu Chou

From: Doug Davis [] 
Sent: Monday, March 30, 2009 2:45 PM
To: Chou, Wu (Wu)
Cc: Asir Vedamuthu; Bob Freund; Li, Li (Li);;;
Subject: RE: [Bug 6692] New: Remove Mode from the specification

  your use-case is a very interesting one.  It shows one of the key points 
that I've been trying to make - this isn't specific to WS-Eventing.  The 
need to send a message through a proxy (and have that proxy be defined by 
someone other than the sending endpoint - the subscriber in your case) 
could be just as meaningful to any EPR.  For example, this could be needed 
for uses of wsa:ReplyTo, or the registrationEPR in WSTX, or the AcksTo EPR 
in RM.  In all of these cases I believe this can be done by doing pretty 
much what you've done below. That is, provide the ultimate destination 
within the NotifyTo EPR but then use some extension mechanism to say "use 
a proxy".   In this particular case I would suggest that you define an 
extension for the EPR structure - then this can be reused in _all_ WS-* 
specs.  For example: 
  <wsa:Address> </wsa:Address> 
  <ext:Proxy> </ext:Proxy> 
You can then also define a mU header that would require it to verify that 
it will adhere to the extension.  IMO, this will not only satisfy your 
WS-Eventing needs but allow for this useful extension to be reused in lots 
of places.  I'm not keen on creating one-off type of solutions just for 
certain WS-* specs - I think its a much better design to create reusable 
components.  For example, should RM create a "use a proxy" extension too 
for its EPRs?  Probably not when the above seems to work just fine for 
both specs. 

 Its also worth pointing out that reusing the extensibility points of EPRs 
is actually a far cleaner design.  In the example you gave it looks like 
the pub/sub code will need to understand this extension. While that is a 
valid choice, it would be much less work for developers to have this 
information encapsulated within the EPR itself.  Then as this information 
is moved through a system only one data structure needs to be passed 
around - the EPR - and the pub/sub code might never actually need to know 
about this extension at all.  In your model below they would need to pass 
around an EPR as well as the proxy information.  And then when the next 
extension comes along they'll need to add yet another.  That a potentially 
large code change each time.  If, instead, they just knew about the EPR 
structure then no code changes will be needed except down at the transport 
layer of the product - where it should be.  At that point they can examine 
all of the bits of the EPR (including the proxy info) and take whatever 
steps are necessary.  This allows for an implementation to be designed 
such that it isolates itself from areas of concern that are of no 
consequence to it. 

STSM |  Standards Architect  |  IBM Software Group
(919) 254-6905  |  IBM 444-6905  |
The more I'm around some people, the more I like my dog. 

"Chou, Wu (Wu)" <> 
Sent by: 
03/30/2009 02:12 PM 

<>, <> 
"Asir Vedamuthu" <>, "Bob Freund" 
<>, "Li Li" <> 
RE: [Bug 6692] New: Remove Mode from the specification

Asir: Many thanks for sharing your thoughts on this issue.  And I attach 
one of our use cases of Mode in WS-E Delivery below. 
- 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 | 
------Use Case of MODE in WS-E Delivery ----- 
Here is a  concrete use case where the  subscriber requests the event 
source to push the  event  notifications through a proxy, obtained either 
through an out-of-band channel (not specified in the Subscribe request, 
e.g. the enterprise registers a special event notification proxy with the 
service provider) or dynamically specified in the Subscribe request. 
Certainly this behavior cannot be conveyed by the wse:NotifyTo. This 
critical use case thus justifies the need for the Mode attribute  in WS-E 
 To indicate the use of an out-of-band proxy, the Subscribe request body 
looks like this: 
            <wse:Delivery Mode=?urn:push_thru_proxy? > 
 To indicate the use of a dynamic proxy, the Subscribe request body looks 
like this: 
            <wse:Delivery Mode=?urn:push_thru_proxy? > 
"Mode=urn:push_thru_proxy" cannot be put into the Delivery extension. This 
is because if the source cannot support "push_thru_proxy", it must fault 
as defined by Mode in Delivery, and the subscriber expects a standard 
wse:DeliveryModeRequestedUnavailable fault. And there is no standard WS-E 
fault for items in the Delivery extension. 

From: Asir Vedamuthu <> 
Date: Sun, 29 Mar 2009 19:59:23 -0700
To: "" <> 

Last week, on the WG conference call, I mentioned that we will provide 
some clarity on the concept of delivery mode (in WS-Eventing) and related 
use cases.

Delivery mode [1] provides a subscriber with a mechanism to specify the 
means by which an event is delivered. Delivery mode is represented as a 
URI in a Subscribe message [2]. The semantics indicated by a delivery mode 

1)  Rules for the delivery of events

a)  Semantics and lifecycle of a Notification delivery

b)  Message Exchange Pattern used (One-way, Request-Response, etc.) and 
how the delivery mode binds to those Message Exchange Patterns

c)  Format of a response (if any)

d)  Configuration parameters or context data (if any) to support the 
Message Exchange Pattern

e)  Rules for the delivery or other disposition of faults generated during 
a Notification delivery

2)  Delivery mode specific protocol information (if any) to guarantee 

3)  Supported delivery formats.

Some portion of the above semantics are captured by an EPR, in a 
machine-readable form, but certainly not all. So, there is value added by 
a formal mechanism to indicate a delivery mode.

The delivery mode is an extension point in WS-Eventing. The WS-Eventing 
specification defines a single built-in delivery mode, Push Mode. Other 
delivery modes may be important for external groups or other W3C Working 
Groups and are delegated to those groups. This is similar to SOAP 
Bindings. The W3C XML Protocol WG defined SOAP Protocol Binding Framework 
as an extension point and a concrete binding, SOAP HTTP Binding (is also 
identified using a URI [3]). Other groups defined SOAP bindings such as 
SOAP-over-JMS and SOAP-over-UDP.

The DMTF WS-Management WG defined three new delivery modes [4] and these 
delivery modes have been widely adopted.

Furthermore, based on the WS-RA WG charter [5], the WG deliverables need 
to satisfy the following requirements as well:

1)  Charter scope - "Mechanisms to allow a subscriber to specify the means 
by which an event is delivered and the definition of a push-based delivery 

2)  Charter scope - "In order to avoid disrupting the interoperability of 
existing implementations, WS-MetadataExchange<>, 
and WS-Enumeration<> should 
remain compatible with protocols and formats that depend on them, and 
offer a smooth migration path from the submission to the standard." We are 
aware of two dependant protocols - DPWS [6] (uses Push Mode) and 
WS-Management [4] (uses Push Mode and, as mentioned before, defines three 
new delivery modes).

[4] - 
Section 7

We hope this helps.


Asir S Vedamuthu
Microsoft Corporation

-----Original Message-----
From: [mailto:] On Behalf Of
Sent: Thursday, March 12, 2009 8:37 AM
Subject: [Bug 6692] New: Remove Mode from the specification

          Summary: Remove Mode from the specification

          Product: WS-Resource Access

          Version: CR

         Platform: PC

       OS/Version: All

           Status: NEW

         Severity: major

         Priority: P2

        Component: Eventing




The concept of Mode is redundant in the current version of the 

All events can be thought of as being delivered. There is no actual 

of "Push Mode" and no other recommended modes. We even have a 

strategy to allow clients behind NATs to fetch events. Likewise, 
strategies for

complex queuing and distribution are supportable without adding additional

modes and are outside the scope of this specification.

Proposal: Remove /s:Envelope/s:Body/*/wse:Delivery/@Mode from the 

and all references to Push Mode. A simple explanation of the delivery idea 

a pointer to some of the techniques available will be needed.


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Wu Chou, IEEE Fellow, Ph.D. | Director |Dialogue System Research | AVAYA | 
233 Mt. Airy Road| Rm. 2D48 | Basking Ridge, NJ 07920 | Voice/Fax: 
908-696-5198 / 908-696-5401 | 

Received on Tuesday, 31 March 2009 16:53:18 UTC