Programming Flex 3

Working with Data Services (Loading Data at Runtime)

Flex applications are generally distributed applications. That means several computers work in conjunction to create one system. For example, all Flex applications have a client tier (discussed shortly) that runs on the user’s computer in the form of an .swf running in Flash Player. In most cases, the client tier communicates with a server or servers to send and retrieve data. The servers provide what are called data services, which are essentially programs that have public interfaces (APIs) whereby a client can make a request to a method of that program. When a client makes such a request, it's called a remote procedure call, or RPC.

There are many types of data services. In its simplest form a data service could consist of a static text file or XML document served from a web server. A slightly more sophisticated data service might be a dynamic XML document generated via a server-side script or program, such as a PHP or ASPX page. Many data services require greater sophistication. One of the most common types of such a sophisticated data service is the web service. Web services use XML (generally in the form of SOAP) as a messaging format, and they enable RPCs using HTTP for requests and responses. Although a SOAP web service is an example of a standards-based data service, many types of data services don’t necessarily conform to a particular standard set by the W3C. Many programs on the Web, for example, expose primitive data ...