Considering the Usage Requirements

There's no free lunch. Some people would have you believe that the Web service does everything for you and that the client does nothing at all. However, the client interacts with the Web service, which means the client must possess some intelligence to perform the task. To use a Web service, you must understand the usage requirements.

From a client perspective, the type of device you use to access the Web service determines the access speed, as well as what you can do with the data once you receive it. Although a PDA such as the Pocket PC can access Google Web Services just fine, you wouldn't want to use it to perform detailed searches or attempt complex activities such as converting data to another language. About the best you can hope for is to perform simple research. On the other hand, a desktop or laptop machine has all of the processing power, screen real estate, and functionality to perform any task. Google Web Services hasn't changed, but the capability of the client has.

Note This book discusses a number of mobile devices. The Pocket PC provides additional functionality and features that make it a better target for some types of applications than devices such as the Palm. On the other hand, most Palm devices are much easier to carry and cost less than the Pocket PC. This book examines the entire range of mobile devices to ensure you understand the limitations of using a specific device to access Google Web Services. I'm not saying one device is better than another—simply that one device works better than the other for a given application.


Google Web Services also has some usage requirements and these requirements might change the way that you use your client. For example, according to the license agreement (see Appendix B for details) you can't make more than 1,000 requests per day—at least, not without special permission. The request limitation ensures the Google servers won't become overloaded, but they also mean you must provide some type of monitoring in your application to prevent abuse of the licensing terms.

Warning If you violate the licensing terms, Google Web Services simply denies your request. In addition, you might receive a message from Google requesting that you adhere to the terms of usage for the Web service.


Often, you can get around the licensing requirements for a Web service by using smart programming techniques. For example, Google doesn't require that you refresh the information you receive at any specific interval. You determine when the information you receive is too old. Using good caching techniques means that you can create applications that are lightning fast, unless the request is new or the data is old. Although it seems as if a 1,000-request limit could cause problems, you can usually satisfy far more than 1,000 requests per day by using smart data caching.