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

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 are:


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 interop

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 mode".

2)  Charter scope - "In order to avoid disrupting the interoperability of existing implementations, WS-MetadataExchange<http://www.w3.org/Submission/2008/SUBM-WS-MetadataExchange-20080813/>, WS-Transfer<http://www.w3.org/Submission/2006/SUBM-WS-Transfer-20060927/>, WS-Eventing<http://www.w3.org/Submission/2006/SUBM-WS-Eventing-20060315/> and WS-Enumeration<http://www.w3.org/Submission/2006/SUBM-WS-Enumeration-20060315/> 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).

[1] http://www.w3.org/Submission/WS-Eventing/#Delivery_Modes
[2] http://www.w3.org/Submission/WS-Eventing/#Subscribe
[3] http://www.w3.org/TR/2003/REC-soap12-part2-20030624/#http-bindname
[4] http://www.dmtf.org/standards/published_documents/DSP0226.pdf - Section 7
[5] http://www.w3.org/2008/11/ws-ra-charter.html#scope
[6] http://specs.xmlsoap.org/ws/2006/02/devprof/

We hope this helps.

Regards,

Asir S Vedamuthu
Microsoft Corporation



-----Original Message-----
From: public-ws-resource-access-notifications-request@w3.org [mailto:public-ws-resource-access-notifications-request@w3.org] On Behalf Of bugzilla@wiggum.w3.org
Sent: Thursday, March 12, 2009 8:37 AM
To: public-ws-resource-access-notifications@w3.org
Subject: [Bug 6692] New: Remove Mode from the specification



http://www.w3.org/Bugs/Public/show_bug.cgi?id=6692



           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

        AssignedTo: public-ws-resource-access-notifications@w3.org<mailto:public-ws-resource-access-notifications@w3.org>

        ReportedBy: david.Snelling@UK.Fujitsu.com<mailto:david.Snelling@UK.Fujitsu.com>

         QAContact: public-ws-resource-access-notifications@w3.org<mailto:public-ws-resource-access-notifications@w3.org>





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

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

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

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 specification

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

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





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