OASIS has recently conferred official "standards" status on WS-Notification, which provides a standardized way for one Web service or other entity to disseminate information to another set of Web services without having to have prior knowledge of those services. WS-Notification standardizes the way Web services interact using "Notifications" or 'Events."'The standards-setting process has performed poorly.'
WS-Notification was designed to work with the Web Services Resource Framework (WSRF) OASIS Standard and the Web Services Distributed Management (WSDM) OASIS Standard.
The WS-Notification OASIS standard (v 1.3) consists of three specifications: WS-BaseNotification, which defines standard message exchanges that allow one service to register or de-register with another, and to receive notification messages from that service; WS-BrokeredNotification, which builds on WS-BaseNotification to define the message exchanges to be implemented by a "Notification Broker" intermediary; and WS-Topics, which provides an XML model to organize and categorize classes of events into "Topics," enabling users of WS-BaseNotification or WS-BrokeredNotification to specify the types of events in which they are interested.
However, some analysts say the newly ratified standard still needs work. Gartner's Roy Schulte and Daniel Sholler posted an advisory that states that the "ratification of WS-Notification advances publish-and-subscribe standards, but falls short of gaining industry consensus. Differences with competing specifications still must be resolved."
The analysts note that publish-and-subscribe communication has been missing from Web services standards, and rival vendor factions initially proposed two partially overlapping specifications for this area -- WS-Notification and WS-Eventing. "Reconciling the differences between these specifications represented a critical test for the standards-setting process, and the process has performed poorly," the analysts conclude.
First, Schulte and Sholler admit they were "overly optimistic" about the timeline of the work, first predicting that a consensus standard could be completed by mid-2005. In the meantime, they say, "work has continued separately on both specifications."
In addition, there is also an ongoing raging debate between two related sets of management standards, WSDM (which uses WS-Notification) and WS-Management (which uses WS-Eventing). "A proposal for WS-Eventing was submitted to the Worldwide Web Consortium in March 2006, but a different organization, OASIS, has now ratified WS-Notification," they observe. "The delay in reconciling WS-Notification and WS-Eventing shows that the Web services standardization process has lost momentum. Standards have remained static for the past year, permitting only primitive interoperability."
Schulte and Sholler do believe, however, that a publish-and-subscribe standard may eventually be achieved -- through the development WS-EventNotification, "which would unify, and remain backward-compatible with, WS-Eventing and WS-Notification." However, ratification of WS-EventNotification may not happen until 2008, they predict. Vendor implementations may also promote adoption of WS-Notification, they add.