Web services for mobile devices can be an effective way to avail mobile devices of server computing power and/or databases, according to an article at IBM's DeveloperWorks website. “Desiging Mobile Web Services” considers when web services are appropriate, before presenting a detailed, technical overview of designing custom web services.

Web services use XML (structured general markup language) and SOAP (simple object access protocol) to distribute applications, offering an alternative to socket communications and messaging techniques. Web services work especially well when application components are written in different languages, author Shu Fang Rui suggests.

Web services do add overhead, however, such as parsing XML and exchanging SOAP messages, and therefore should not be used in real-time and performance-critical applications. Neither should they be interposed between separate application layers, such as the control and display layers, Rui says.

After helping users decide if Web services are of interest, Rui's article discusses the following topics:

• Manage the granularity of your Web services
  
• Define the Web service interface first, then implement it
  
• Use Document/literal as your encoding style
  
• Give preference to JavaBean components over Enterprise JavaBean (EJB) components as the service provider
  
• Avoid deep nesting of XML elements that may greatly prolong the time of parsing, marshalling, and demarshalling

The complete tutorial can be found here.

 
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