I'm confident that by now everyone has heard something about Microsoft's recent introduction of its .NET technologies. If you haven't, check out Microsoft's .NET site and MSDN Online's .NET information. As you learn about .NET, you'll see that Microsoft is positioning these technologies as the next generation of Windows services on the Internet.
You might wonder how Microsoft .NET applies to XML. According to "About .NET," a Microsoft white paper, the framework that supports .NET is "an XML compound information architecture that integrates browsing, communications, and document authoring."
Because XML is .NET's underlying communication protocol, a basic understanding of XML is a prerequisite to learning about the new Microsoft technologies. Don't think of XML as something you need to create by hand; vendors are releasing a plethora of tools that work with XML. Microsoft recently released the Simple Object Access Protocol (SOAP) toolkit for Visual Studio, available on the MSDN Online Web Workshop site. In addition, attendees of the Microsoft Professional Developers Conference (PDC) earlier this month received the BizTalk Server beta release and the developer preview of Microsoft's Visual Studio.NET tools. The primary reason you'll want to understand XML is that XML is the basis for SOAP, and SOAP drives the upcoming .NET services.
SOAP is an example of a technology built within the XML framework. SOAP is a common set of rules for representing and extending data and commands. However, as you look into .NET, you'll see that SOAP doesn't operate independently. Related protocols (such as the SOAP Contract Language—SCL, which implements Remote Object Proxy Engine—ROPE, and SOAP Discovery) support SOAP. Each of these technologies builds on XML and lets you use SOAP in a distributed manner.
SCL defines a contract to which the SOAP objects on a server will adhere. SCL lets you turn that contract into a proxy against which you can program. Various systems will use SCL to describe the interfaces of the SOAP objects they support. The World Wide Web Consortium (W3C) is reviewing the SCL specification. While the W3C reviews the SCL standard, the .NET platform references a similar technology called Service Description Language (SDL). When the SCL specification is finished, .NET platform tools will use SCL to implement "SOAP on a ROPE."
Clients will use the SOAP Discovery protocols to identify a server that supports a desired service, then send an SCL (or SDL until SCL is finalized) query request to the remote server. The remote server then can supply an XML-formatted SCL message to the client that describes how to work with the server-provided SOAP objects. At this point, clients use ROPE to communicate with what's known as a Web Service.
According to .NET documentation, the Web Service is important to the Internet's future. As described above, its capabilities come from using SOAP, which builds on XML-formatted messages.
Many people wonder what role XML will play on the Web and how much data will be in XML format. As the Internet changes, we'll see how the XML format goes beyond packaging data to making the Internet a rich, interactive environment.