1 WS-Notification Overview Alan Weissberger NEC-Labs America GGF11 June 8, 2004

2 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

3 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

4 WS-N History (continued) April 21 Interop event at IBM, RTP, NC April 29 1 st 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 nd meeting of OASIS WS-N TC at Fujitsu-UK, near Heathrow airport. [WS-RF meets previous 2 days]

5 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

6 3 players: Subscriber, Producer, and Consumer of Notifications

7 Subscription Request to a Notification Service

8 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

9 4 th Player: the Notification Broker -an Intermediary that processes subscription requests and re-directs notification messages to the designated consumer(s)

10 Pub/Sub example of Brokered Notification Broker receives subscriptions and redirects notifications

11 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?

12 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

13 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?

14 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: 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

15 More information on WS-N WS-RF and WS-N Update at GGF11- June 8 th 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 archives, documents and specs; participate in telecons, f2f meetings, discussions, etc.