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A new direction for Web services. (Schema Language).

Article Excerpt
Web services is a glamorous term for a very old and established idea. The core Web services technologies, SOAP and WSDL, allow developers to define new protocols. A protocol is nothing more than a way for computer programs to talk to each other over computer networks. As long as there have been networks there have been protocols. What makes Web services unique is that they're the first mainstream technologies, supported by all major vendors, intended to make the creation of new protocols so easy that ordinary business developers can do it.

Developers who, for instance, build a SOAP wrapper around their payroll systems may not think that they're building their own protocol, but in fact they are. Web service developers must decide how to group their logical objects into services. They must create some technique to correlate messages sent to the service with particular objects. They must choose which messages may be sent to which objects. For each message they must choose whether or not it should be sent in a manner that expects a reply. They must choose an XML representation for the message. These are the decisions that would usually be made by a so-called "application protocol" like SMTP (Simple Mail Transfer Protocol), FTP (File Transfer Protocol), or HTTP (HyperText Transfer Protocol).

I claim that there are two problems with this picture. First, making new protocols is still not easy enough for ordinary developers to do. Today's tools only make it seem easy by removing or hiding many options...