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WS-Notification Overview

Alan WeissbergerNEC-Labs America

1 408 863 6042

GGF11

June 8, 2004

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Purpose and Mission of OASIS WS-N TC

• Define a set of specifications that standardize the way Web Services interact using the “Notification pattern.”

-provides interoperability between different pub/ sub messaging middleware providers

-notification pattern may be used in systems or device management, or in commercial apps like electronic trading

• Leverage off the 3 specs and white papers submitted by various co-authors

http://www.oasis-open.org/apps/org/workgroup/wsn/

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History of WS-N

• Introduced in Jan 04 at Globus World, as part of the WS-RF package to replace OGSI.

• Feb 25 Feedback workshop on monolithic WS-Notification spec. Intent to form an OASIS TC. Spec later sub-divided.

• March 5: Steve Graham splits WS-N into 3 specs: WS Base Notification, WS Brokered Notification, WS Topics

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WS-N History (continued)

• April 21 Interop event at IBM, RTP, NC• April 29 1st meeting of OASIS WS-N TC;

[WS-RF TC met the previous day] in New Orleans, LA

• May-June Bi-weekly conference calls --------------------------------------------------------• Next f2f: July 29-30 2nd meeting of OASIS

WS-N TC at Fujitsu-UK, near Heathrow airport. [WS-RF meets previous 2 days]

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The Notification pattern • A Web Service (WS) or other entity (“producer”)

disseminates information to a set of other WS’s (“consumers”), without having prior knowledge of these other WS’s

• The “consumers” are registered with the “producers” either directly or via a subscription agent (“subscriber” or “initiator”).

• Subscriber sends a “Subscription Request” message to Producer/Broker; an End Point Reference (EPR) is returned (defined in WS Addressing spec) to confirm the subscription

• Both direct and brokered notification are possible and are dealt with in different specs

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3 players: Subscriber, Producer, and Consumer of Notifications

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Subscription Request to a Notification Service

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The Subscription Process• A Subscriber sends a Subscribe Request message to a

Notification Producer in order to register the interest of a Notification Consumer for Notification Messages related to one or more Topics.

• Notification Producer MUST (???) create a Subscription resource representing the Subscription

• Producer returns an Endpoint Reference* in the response to the Subscribe request. This EndpointReference is a WS-Resource-Qualified Endpoint Reference and includes the address of a Subscription Manager service and a reference property containing the identity of the Subscription resource.

* At the April 29 f2f meeting, Oracle challenged the use of EPR and proposed another mechanism submitted to W3C

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4th Player: the Notification Broker-an Intermediary that processes subscription requests and re-directs

notification messages to the designated consumer(s)

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Pub/Sub example of Brokered Notification

Broker receives subscriptions and redirects notifications

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Dependency of WS-N on WS-RF?

• There are 2 relevant WS-RF specs for WS-N: WS Resource Properties and WS Resource Lifetime (destruction only)

• Key question: can direct (non- brokered) notification exist without these 2 specs:

-for pub/sub systems? -for Grids using stateful resources

associated with the web service(s)?• What is the implicit resource pattern?

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Relationship of WS Agreement to WS-N and WS-RF specs?

• On its own, WS Base (direct) Notification includes a “lightweight” subscription agreement, but only for dissemination of notification messages (typically on a state change or some number of designated event occurrences)

• When WS-N is combined with WS Topics, WS Resource Properties, and WS Resource Lifetime, it has the potential to be a more robust, comprehensive agreement (depending on the types of resources available)

• Some WS applications may use that package, rather than WS Agreement, to subscribe to a Web Service that produces notification messages

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What are Topics used for?

• Used by a subscriber to identify the subject area it wishes to cover in a subscription– A Producer/Broker only delivers if notification of the list of topics

associated with the subscription, intersects with the list of topics associated with the message

• Used to identify the set of subjects that a given Producer/Broker deals in– Useful information for a prospective publisher or subscriber– A producer may support only one topic

• Can be associated with metadata– Notification message schema– Semantic information

• Could be used as part of an access control scheme or in conjunction with WS Agreement?

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Status of the WS-N documents

• WS Base Notification - to be voted on during the June 7, 2004 telecon (Editor: Steve Graham of IBM)

• WS Brokered Notification – draft available (Editor: Dave Chappell of Sonic Systems)

• WS Topics – no draft yet. Pre-OASIS TC draft:

http://www.oasis-open.org/apps/org/workgroup/wsn/download.php/6600/WS-Topics-1-0.pdf

• Also a ppt presentation by Peter Niblett at April 29 f2f meeting

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More information on WS-N

• WS-RF and WS-N Update at GGF11- June 8th 12:30PM: Presented by David Snelling of Fujitsu, co-chair of WS-RF TC

• Join the OASIS WS-N TC as either a prospective member (must attend telecons) or observer: get access to email archives, documents and specs; participate in telecons, f2f meetings, email discussions, etc.