eXtensible Markup Language, XML

The sections below cover the fundamentals of XML and offer explanations of how it should be deployed. To go directly to a section, click on one of the links:

What is XML?

The eXtensible Markup Language (XML) is a language for representing data. Quite simple, really. It looks a little like HTML, in that it uses tags (like <this>) to structure and format the data. It is simpler than HTML in that it does not define specific tags, but it is more complex in that it requires the tags to be defined. OK so far?

The simplicity of XML is its strength. It can be used for everything from legal documents to comic strips (the preceding article quite rightly coined XML “The Tupperware of the Internet”). Rather than re-invent the many descriptions of XML out there, here are some that others prepared earlier. A brief, for-dummies description of XML’s purpose is given here, and a longer one is here – the latter descends into document formatting standards (such as SGML) but the first sections are useful background. Finally we have the excellent XML in 10 points from the W3C.

If you want more detail on the language itself, there is a tutorial introduction here. Further training resources are provided in the article here, which compares four online XML training offerings.

The Business Benefits of XML

Clearly, as XML is just a language it has many potential uses. Its strength lies in its standardisation – if more than one party agrees to use XML (and, what is more, agrees on the format of XML to be used), then the two parties can communicate. For a summary of the business advantages of XML, see the article here. XML also overcomes many of the limitations of HTML, as listed here.

Three application areas are exploiting this strength, each with its own benefits to business: these are content management, business-to-business (B2B) e-commerce and Web services.

Content Management – a summary article from the Cutter Consortium is here.. We cover this in more detail here.
B2B E-Commerce – to see how XML stacks up to meet four challenges of business, click here. Benoit at Pineapplesoft has put together a commentary on the use of XML in e-commerce, titled The XML Economy
Web Services – XML is a fundamental element of the Web services framework, along with UDDI and SOAP. We discuss this further here.

Finally, XML has a place in business re-engineering, as described here.

Deploying XML in the Corporate Environment

The paper here explains the problems that need to be solved in an XML deployment for B2B e-commerce, and how to overcome them.

Issues with XML

What could possibly be wrong with XML? After all, it is just a formatting language. The answer lies in Bananarama’s first law of IT – “It’s not what you do it’s the way that you do it: the risks with XML are not so much with the language itself, rather in how it is used. If nothing else, remember the adage “real programmers can write FORTRAN in any language.”

There is an industry fear that “simple” XML will become SGML as new capabilities and features are added to the language to support more complex constructions and data types. An article here is indicative of the convolutions, as it is a little convoluted itself. However most of us will not care, as long as the message gets passed. XML is only the messenger.

Finally, the corporate wrangling about how XML is used will be a problem for as long as it continues, not least because it slows down the adoption (and hence evolution) of the language. An article about this is here.

The Future of XML

Where is XML going? It has already achieved the widest possible adoption among the vendor community. The next step, then, is to achieve widespread use. The message formatting standards are being agreed on an industry-by-industry basis, but as discussed in Issues with XML there are some hurdles still to be overcome.

Further Resources on XML

Startkabel’s XML page is probably the most succinct, complete set of links about XML, ever.