The interaction between flex application and DataService

Flash Player supports any text data, XML, a binary messaging format called
AMF, and persistent socket connections, allowing for real-time data pushed from the
server to the client.

Each data format Flex supports may or may not require special server resources. For
example, a Flex application can request XML data from a static resource or from a
dynamic resource such as a PHP page. AMF is a binary messaging format that Flash
Player understands natively, but for a server to interact with Flash Player via AMF, it
requires an AMF translator on the server, such as the remote object services that are
part of Flex Data Services.