This chapter discussed Web services and applications within the context of mobile and wireless environments. The common availability of wireless cellular networks and wireless LANs together with advancements in highly integrated semiconductor components is enabling a wide array of mobile and wireless devices that are extending the reach of enterprise information "into the field."
The development of Web services-based applications that can run on mobile devices requires special thought. Mobile applications can access remote Web services either directly or through a proxy server. Using a proxy server to access Web services effectively creates a higher-level coarse-grained interface to the underlying Web services. This reduces usage of the wireless network and can favorably impact cost, performance, as well as power consumption. In many cases, where a non-mobile implementation of the application already exists, a proxy server-based Web services invocation is reasonably easy and straightforward, thus reducing development costs and time-to-market.
For some situations, direct invocation of Web services from mobile application is warranted. If the mobile platform is sufficiently robust, the application can generate and parse SOAP messages using standard SOAP and XML parsers. Alternately, more efficient and smaller footprint platforms such as kSOAP and kXML can be used.