To those bewildered by the seemingly endless number of Web services standards that begin with "WS-," things just got a little more confusing.
This week, IBM, Hewlett-Packard Co. and others announced the creation of a proposed Web services standard called WS-Notification, which allows messaging systems to generate notifications of Web services "events," such as when a purchase order is ready to be processed.
If this sounds like familiar ground, that's because it is. Earlier this month, Microsoft, BEA Systems Inc. and others announced that they had authored a specification called WS-Eventing, which is designed to do the same thing as WS-Notification. However, there are differences in the ultimate aims of the specifications, according to those who've looked at both.
First and foremost is that WS-Notification is intended to blend Web services, a set of technologies for connecting and reusing applications via a network, with grid computing. "Grid" is the term for pooled computing resources that an enterprise can tap into as needed.
A matter of priorities
While grid computing isn't something that Microsoft is pushing right now, it's very much a part of IBM's on-demand strategy.
"There are some specific needs for notification in grids that Microsoft and others didn't want to consider," said Ronald Schmelzer, a senior analyst with Waltham, Mass.-based ZapThink LLC. "So, basically, IBM had some priorities for their event messaging spec that weren't priorities for Microsoft and others."
Another difference involves the management of these event notifications. Mark Potts, who holds the title of "distinguished technologist" at Palo Alto, Calif.-based Hewlett-Packard, said that, while the grid aspect of the notification standard is important to HP's adaptive enterprise strategy, giving its customers the ability to manage events through its OpenView platform is even more important.
"The reason that HP really went with the [WS-]Notification subscription is that, from our perspective -- from a management perspective, we really needed something that was a little bit richer than a peer-to-peer event mechanism," Potts said. "And I really think Microsoft came at it with a peer-to-peer perspective."
'Pub-sub' for the Internet
Among the other companies involved in the creation of WS-Notification was Sonic Software Inc. of Bedford, Mass. In a weblog posting on Wednesday, Dave Chappell, vice president and chief technology evangelist for Sonic, put his own spin on the proposed standard.
"I would best describe WS-Notification as 'pub-sub' (publish-subscribe) for the Internet," he wrote. "It's a distributed broker-based pub-sub using Web service interfaces.
"It doesn't directly address QoS (quality of service) issues such as exactly-once delivery, although it is intended to be composable with WS-Reliable Messaging. In fact, it's intended to be composable with the rest of the WS set of specs."
A set of related specifications -- WS-Resource Properties and WS-Resource Lifetime -- were announced at the same time as WS-Notification. Together, the resource standards, also authored by a group led by IBM, have been dubbed the WS-Resource Framework.
The WS-Resource Framework
WS-Resource Properties defines how data associated with a stateful resource -- a resource mindful of related messages -- can be queried and changed using Web services technologies. This allows companies to build applications to read and update data associated with resources, such as contracts, servers and purchase orders.
WS-Resource Lifetime allows users to specify the period during which a resource definition is valid. For example, WS-Resource Lifetime can automatically update suppliers from all systems when contracts or service-level agreements expire.
So, what do all of these WS-related specifications mean to users? Not much, said Schmelzer, of ZapThink. "Our concern is that we're seeing a little bit of a spec glut," he said. "Customers don't implement specs, they implement products."
Schmelzer said that it can take a year or more before specifications find their way into software products. That's true of WS-Eventing, which probably won't make its debut in a product until Longhorn, the next version of Microsoft's Windows, comes out in about 2006, he said.
HP's Potts was a bit more optimistic about WS-Notification. Potts, who was chief technologist for Talking Blocks Inc. before it was acquired last year by HP, said that work to integrate WS-Notification and the WS-Resource Framework into HP's management software platform could begin within the next two quarters.
Before then, the specifications will be tested and then submitted to one of the major standards bodies. Which standards organization will be chosen is still unclear, although Potts said that it's likely to be the Organization for the Advancement of Structured Information Standards, or OASIS.
Coincidentally, a standards organization to hash out WS-Eventing hasn't been chosen either, but Potts speculated that job will end up at OASIS as well, because of that group's work on other specifications related to the reliability of Web services.
And both Potts and Schmelzer said that, because of the similarities of WS-Eventing and WS-Notification, the two will likely be blended into a single specification eventually.
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