So, what will it take to put such applications in hand?
Mobile applications must be designed to compensate for devices' limited size and power. For that reason, Web services would seem like a perfect fit for mobile users--letting them identify and use highly specific services on an as-needed basis rather than storing gobs of data and applications on their small devices. However, there are a number of problems with Web services technology that limit its potential for mobile users.
Web services technology involves the transfer of data from large documents (in addition to the overhead related to Web services technologies themselves) that can easily overburden the limited bandwidth available to mobile devices using ad hoc wireless network connections. Even relatively simple operations require the transmission of much more data than is necessary with compact binary code performing the same operations. "Despite the rollout of 2.5G networks, mobile bandwidth remains limited compared to a LAN, a wireless LAN, or server-to-server Internet connections," says Giga Information Group Vice President Carl Zetie. He points out that the bandwidth of current and emerging wireless services is still measured in tens of kilobits per second, and that network limitations won't be completely addressed until true 3G networks are available that offer each device megabits per second of bandwidth.
Even when bandwidth limitations are eventually overcome, large documents will still be an issue for mobile devices. The large size of Web services documents will easily swamp the limited memory, storage, and processing capabilities of small handheld devices. For example, a mobile CRM user might activate a Web service that yields hundreds of detailed customer records that can be managed on a desktop computer but can't be stored or manipulated by a handheld device or Web-enabled telephone. The solution? Redesign the application so that it doesn't send lots of records to mobile users. Even if the records were reduced, though, the design of current Web services architecture would mean that there would still be considerable overhead in this and other cases.
The small screens and restricted input capabilities of mobile devices are also limiting. "You have to configure a Web service for use on a mobile device, particularly the input and output. You can't expect a handheld user to view big documents or put in long sentences of data," says Meta Group Vice President Jack Gold.
The design of Web services also assumes that fast and reliable network connections will be available--and that won't be the case for some time. To use Web services, devices rely on processes for service discovery and negotiation that require multiple round-trips over the network--a process that's too slow for mobile users' wireless connections.
Web services also use a synchronous design (or must at least acknowledge receipt before asynchronous processing) that assumes a network connection is constantly available, as it is with most LANs. However, because mobile applications can't depend on uninterrupted network connections, they're optimised for asynchronous exchanges and intermittent connections. Giga's Zetie points out that although 2.5G networks are fast enough to handle synchronous processing, they must still establish a connection, which can eventually time out due to inactivity or processing limitations in the mobile device. He says that even pure 3G networks will confront coverage limitations, which means that mobile application developers will still need to design their applications to work asynchronously and to handle service interruptions.
Mobile extensions are being developed for the two leading Web services technology platforms--Java and .Net in the form of Java 2 Platform, Micro Edition (J2ME) and .Net Compact Framework, respectively. Both architectures are being designed to mitigate some of the limits of mobile computing but are unlikely to provide many of the features usually associated with Web services technology. "It's too early to tell with J2ME and .Net CF, but the good thing is that they both support offline functionality," says Dennis Gaughan, research director at AMR Research.
Although it will be some time before Web services standards are ready for mobile applications, enterprises can still experiment with limited applications. Giga expects some enterprises to begin using lightweight XML-based remote procedure calls long before full-blown standards emerge to ease future migration for mobile Web services applications. But beyond this, enterprises will have to wait for Web services to mature before this technology can really expand the capabilities of the mobile enterprise.
What do you think it will take for Web services to deliver corporate applications to mobile devices?
