Sun Dreams of Jini for Web Services

Claims dynamic network architecture not just for devices, suitable for discovery, delivery

By Edward J. Correia

March 1, 2002 —

Since 1999, Sun Microsystems Inc. has been telling the market that Jini, its dynamic network communications architecture, was designed mainly for devices. Now the company is repositioning the technology, saying that it's also a suitable framework for developing and publishing software services.

"What was picked up on the launch was a very device-centric message. That was half the story," said Franc Romano, Sun's group marketing manager for Jini, who is now offering Jini as an implementation solution for what the company calls Services on Demand, a concept that encompasses all service delivery over a network, including Web services.

"For instance, a printer is a device that provides printer services," he said. Romano went on to claim that Jini's lookup service is a more feature-rich method of facilitating Web service discovery than UDDI. "They are different ways of providing similar functionality; both serve directory functions."

Unlike UDDI, asserted Romano, Jini is dynamic, and can discover and deliver additional information about the devices or services it finds. "Jini provides logic code that encapsulates instructions on how to work with that device or service. And Jini is the only technology that can pass objects over the network; UDDI can only accommodate character strings," and not device drivers or executables.

Chris Kurt, group program manager of UDDI and Web services at Microsoft Corp. who sits on the board of UDDI.org, argued that comparing UDDI to Jini is "like comparing apples and oranges. It would be a pretty big challenge for us to line UDDI up with Jini; the points of the technologies are so different. What [UDDI] passes back and forth is a set of SOAP XML requests. I guess technically they are strings. But inside, there is information about the services and protocols that UDDI stores or provides references to."

Those references could be used to point to drivers, and the drivers could then be downloaded, according to Tom Glover, program manager for Web services and standards at IBM Corp. who's also with UDDI.org. "It may be possible to use Jini to mimic UDDI to allow someone to discover and access Web services, in the same way it may be possible to use UDDI to discover and get access to system devices. That doesn't mean they are good at doing each other's jobs." Glover said that early in UDDI's life, there were comparisons drawn between Jini and UDDI. "People said, 'Maybe UDDI is a better Jini,' but our answer was that it's not. Jini and UDDI are designed to do fundamentally different jobs, so the data structures and mechanisms in the two are very different."

But Romano maintains that Jini can serve as a better UDDI than UDDI. "Jini permits services to register as Java types rather than by a simple string or name," allowing services to be categorized rather than simply listed. The benefit, Romano explained, is that if a client is looking for a printer, a lookup of all available printers can be requested. "The client can then choose by whatever printer criteria they want, rather than having to know that a certain type and model of printer is available" and what its name is.

Simon Phipps, Sun's chief technology evangelist, summed up the differences in terms of client/server and peer-to-peer. "If you walk into a room with your wireless device and want to turn on the light, you shouldn't have to query a UDDI server in Taiwan for instructions. Rather, it would be better to interface with a local node, or directly with the switch itself."

Steven Knudsen, CTO and co-founder of embedded software developer PsiNaptic Inc., explained how his company takes advantage of Jini's ability to pass objects. "With Jini, that object can be a driver. For small devices that often are mobile, you can utilize [device] services as you enter a location and unload [the driver] when you leave."

PsiNaptic uses Jini to develop JMatos, a small footprint operating system for mobile phones, handheld computers and medical and automotive systems, all of which can interoperate. According to Knudson, Sun's solution was the only suitable one available. "The question was, 'How do we get devices to communicate spontaneously with each other?' We looked at other protocols like UPnP and OSGi. We knocked UDDI out quite quickly; it didn't go far enough for what we wanted to do."

Romano said that Jini (www.sun.com/jini) is best at handling change. "Jini really shows its advantages over [UDDI] when you get into highly dynamic environments where there is constant change in the computing environment or the network."

Backing up that claim is Jim Edmiston, CTO and co-founder of Eko Systems Inc., which uses Jini to build add-on devices that network-enable medical monitoring equipment. "In the health-care environment, workers need to be able to add more nodes as needed as a patient's condition changes. We have nodes that go into operating rooms and recovery units, that roam around on carts, and that people plug in and use during an operation. The importance of Jini's dynamic capabilities cannot be overstated. And while we might accept the fact that Microsoft Word crashes once in a while, in an operating room that just can't happen."

Ironically, Sun has not made Jini a part of its Sun ONE Web services strategy, despite its purported benefits. "This is primarily because we're still considering [Jini] emerging technology, and Sun ONE is very much [about] what exists today," said Romano, adding that although 75 commercial implementations are promising, Sun would want to see wider-spread acceptance before it would be willing to adopt the technology itself. "We need to continue to test the validity of the concept and to exemplify how Jini can be used."

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