Short for Extensible Markup Language, XML became a World Wide Web Consortium (W3C) recommendation in 1998 as a slimmed-down version of SGML. Designed with Web documents in mind, XML enables developers to create customized tags, which is what makes them extensible. These tags allow for the definition, transmission, validation and interpretation of data between applications and organizations. And it has become the core of Web services, thanks to XML’s rapid and widespread adoption by the corporate IT world.
According to Kirk Farquhar, director of systems engineering at Borland Canada in Toronto, the entire concept of Web services is hinged on XML.
“You couldn’t do Web services on a vendor-to-vendor basis without having XML, and if it wasn’t there we would have had to invent it,” he said. “The alternative is to have everyone ask each other what file format needs to be sent. Web services using XML allows you to do business electronically with someone you’ve never had a conversation with.”
It is XML’s extensibility that serves as the key for the success for Web services, according to Thomas Murphy, program director of application delivery strategies at Meta Group Inc. in Temecula, Calif.
“XML provides the foundation for creating the rest of the whole stack that has become Web services,” Murphy said.
The other important aspect of XML is that it is very data oriented at its core, he said.
“It’s built to define things – it defines message constructs, it defines data, whether in the classic sense in a database or about a service provided. It defines anything that needs to be defined and forms a contract between two communicating computers,” he said.
Farquhar expressed the value of XML in terms of its ability to encapsulate data with identifying tags.
“Putting it into a non-IT perspective, it’s like looking at languages of the world: reading in Japanese and English and Russian is difficult because they each use a completely different alphabet. It’s difficult to even sound out words, but if you use a translation dictionary to go from Russian into English, it uses the Roman alphabet as a link to help you sound things out,” Farquhar said. “XML becomes the Lingua Franca for moving data.”
Pierre Mullin, senior consultant and partner at Syntact Consulting in Halifax, has been using XML on a wide range of projects over the past few years, and views its rapid uptake within the developer community as an acknowledgement of XML’s ability to create better software solutions.
He does not, however, see a similar movement to latch onto Web services. Despite the buzz around it, Mullin doesn’t foresee the necessary infrastructure popping up anytime soon.
“I think we’ll tend to see things that look like Web services, but with more of a roll your own infrastructure,” Mullin said.
Because the notion of Web services is still in its infancy, Murphy predicts that a number of new standards are going to be proposed around XML, citing ebXML and EDI as examples.
“The good thing about this whole area and time is that it’s like the Internet when it first came out. There are a whole lot of different innovations, ideas and thoughts. XML’s a simple, basic technology like HTML, but it provides options to do different things. There are tons of different ways to apply the technology because of its simplicity and flexibility. Web services is all because of XML,” Murphy said.