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A Web Services Strategy for Mobile Phones
by Nasseam Elkarra | Pages: 1, 2

SMS Workarounds

Most wireless carriers allow anyone to send SMS messages to their customers via email. Although users cannot reply to the sender of the email, this is useful for notification messages. You have to be a "premier partner" to be able to send and receive, but the average programmer can use an SMS Broker to have the same access without going broke. SMS Brokers partner with a cellular service provider and then lease access to developers. Simplewire offers one such development environment for creating and testing your wireless messaging application. They have a free evaluation version and they also offer paid commercial deployment packages. ActiveBuddy's BuddyScript SDK is very complete solution for developing, testing, and deploying your interactive agent. The BuddyScript SDK includes its own scripting language, IDE, server for deploying agents, and much more. You can launch your interactive agent to mobile users via SMS and WAP without setting up a relationship with a wireless carrier. The BuddyScript Server included in the SDK can exchange data via SOAP over HTTP. The only downside to the BuddyScript approach is that you are pretty much tied in to their development platform.

For the tech savvy, you might be able to buy a data cable for your GSM phone and, with the appropriate software, process the modem commands. Of course this is not suitable for a commercial application, but they do have dedicated GSM modems. So, theoretically, you can get a personal account with a wireless GSM carrier, take out the SIM card, put it in a dedicated GSM modem, and hack your way through to make it work. And, on the subject of hacking, I must mention Kannel, an open source WAP and SMS gateway.

VoiceXML

Accessing web services with VoiceXML has never been easier using BeVocal's JavaScript SOAP API. The BeVocal Cafe is an excellent place to get started; it offers a phone number you can call to access your application as well as documentation, samples, and tools.

Earlier I mentioned how Tellme offers access to voice driving directions using the MapPoint web service. Tellme also offers a robust development environment for developing VoiceXML applications. Unlike BeVocal, Tellme does not have built-in support for SOAP. You would have to roll your own Javascript Library or you could forward the input to an external application with SOAP support (e.g. a CGI script or Servlet) and then have that application generate VoiceXML back to the client. Have you ever picked up the phone only to hear an automated message? The telemarketers are getting lazy, but now you too can bug people with Tellme's Notifier service which allows your VoiceXML application to initiate the call to your clients. The Notifier service can be useful for reminders of appointments and other types of asynchronous messages.

WAP

Since you cannot view WML on regular browsers, you will need a WAP browser emulator for testing your WAP applications. WAP also allows applications to initiate sessions through the use of the use WAP Push Access Protocol. By creating push-enabled applications, you can implement asynchronous messaging. Openwave provides a WAP Push Library as part of its Openwave Mobile Developer Toolkit (OMDT). The OMDT is an excellent place to get started with its inclusion of emulators, messaging APIs, and support for the latest technologies in the mobile world. Nokia also has an excellent resource page that has tools and documents to help you get started.

If you don't have access to a WAP gateway don't forget about the open source Kannel project. The open source crowd will also enjoy Enhydra's open source Java/XML application server. Although you can serve up WML pages using any Web server, Enhydra provides an excellent framework for separating presentation from code. Using Enhydra's XMLC, you can convert a specially formatted WML document into objects that you can access from your Java code.

J2ME

The Wireless Messaging API (WMA) package gives you access to SMS functionality but there are third party packages that are more suitable for XML messaging. kSOAP, another open source project from Enhydra, is a lightweight SOAP implementation suitable for J2ME. If you think SOAP is too bloated and want to shave off some overhead, Enhydra also has an XML-RPC implementation (kXML-RPC project). For the Java RMI and JMS fans out there, there is a J2ME RMI optional package and a commercial wireless JMS solution available. To speed up your development efforts, you might want to consider using one of several SDKs available. Sun and Nokia's toolkits can run as standalone tools and also integrate into SunONE and JBuilder.

.NET Compact Framework

The .NET Compact Framework provides a robust environment for developing mobile applications. In traditional Microsoft point-and-click fashion, you can have an application running with minimal effort. If you are a .NET developer, you will enjoy its .NET Framework heritage and its integration with Visual Studio .NET. The .NET Compact Framework will definitely have its biggest impact in the PDA market where Windows enjoys some success. The downside is that the .NET Compact Framework has no market share whatsoever in the mobile phone space and it will try to break into a tight market.

Conclusion

With the availability of packet-switched, always-on networks for mobile phones becoming more widespread, mobile access to data will become easier than ever. web services seem like the natural solution for integration problems, but mobile phones do not have the privilege of guaranteeing support for the core web services technologies. However, you can still effectively deploy a web service for mobile clients by deploying a client interface using existing technologies available. Technologies such as SMS, WAP, and VoiceXML can be utilized to make this possible. As more mobile phones support J2ME, you can even choose to deploy a pure SOAP client without the need for a middleman.

SMS Workarounds

VoiceXML

WAP

J2ME

.NET Compact Framework

Conclusion

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