What is it?
The Extensible Markup Language (XML) is promoted as the universal language for e-commerce. It enables business partners' IT systems to talk to one another by exchanging documents that can be acted on at the process level, rather than data level. However, firms currently need to agree which version of the many variants of XML to use. There are a number of initiatives to develop wider XML standards.
Where did it originate?
Like HTML, XML evolved out of the Standard Generalised Markup Language (SGML). Unlike HTML, it kept much of the functional richness of its parent, while greatly improving ease of use.
What is it for?
XML has been described as "a clean, cheap format for sharing information".
Many commentators are worried that its simplicity is being buried by too many features, and that the language is being "Balkanised" into dialects. These have difficulty communicating with one another. Most see the World-Wide Web Consortium's (W3C) XML Schema as a way of pulling XML back together, but some believe its adds to the complexity.
Further complications come from the organisations competing to establish commercial XML standards. The Electronic Business XML Initiative (EBXML) was set up to standardise electronic contracts and trading partnerships.
The Universal Description, Discovery and Integration Initiative (UDDI) was founded by Microsoft, Ariba and IBM, who couldn't wait for EBXML. It is designed for large corporations.
RosettaNet was set up by the IT and electronic component manufacturing communities. Then there's Microsoft's eBiz, and the XML-based Simple Object Access Protocol (Soap).
What makes it special?
It is cheap (or free), quick to develop, and flexible enough to be used almost anywhere. XML parsers and tools can be downloaded for nothing.
XML's Document Type Definition (DTD) offers the means to define a specific XML document structure. The DTD needs to be accompanied by a description of the purpose of each defined element and attribute - the semantics.
Businesses must agree the structure and the semantics to be used for e-business.
How difficult is it?
Much easier than SGML, more demanding and more rigorous, than HTML.
Where is it used?
XML's acceptance is almost universal, although doubters are becoming more vocal. Mike Thompson, an analyst with Butler Group, warns that, with the need to translate thousands of different tag sets, it is debatable whether XML is even a standard.
What does it run on?
Most suppliers support XML.
Not to be confused with
A T-shirt size.
Few people know that
The term "XML time" has been coined to describe the speed at which new specifications are being released. It is even faster than "Internet time", which reduced the old product development cycle from two years to three months.
As you might expect, the Web is awash with free XML tutorials of varying quality. Start with the World-Wide Web Consortium ( www.w3.org). Try also www.findtutorials.com, which has hundreds of offerings, although they are unvalidated. You might feel safer with major suppliers such as IBM, Sun or Microsoft.