Someone suggested to me recently that XML (eXtensible Markup Language) will have a similar length of life as COBOL (the original Common Business Oriented Language - which wouldn't be a bad alternatively name for XML) – and given that COBOL has been around since 1960 and is still going strong, it suggests that XML will be around for quite a while! XML is the son of, and a subset of SGML the Standard Generalized Mark-up Language. SGML is very powerful, especially when compared to HTML but perhaps too complex, especially for web use. So, in 1996 it was decided that there was a need for something between HTML and SGML and hence XML was conceived. XML offers a simple, extensible, but well structured way of describing datasets. The big thing about XML however is the take up. More and more systems now support XML mostly because of its combination of power and simplicity - it is even an integral part of Microsoft Office 2003 for example, you can save Microsoft Word and Excel files as XML.
It is relatively simple to map different XML "dialects" (i.e. different sets of tags denoting different data definitions) via eXtensible Stylesheet Language (XSL). The benefit of this is the ability to flexibility to map different vocabularies or taxonomies together using custom XSL. There are an increasing number of agreed industry specific transformations and the growth in these will make life easier – however as with any "standards" –One growing example is XBRL (Extended Business Reporting Language – see XBRL.ORG.) – Which is establishing itself in the growing area of compliance reporting.
So is XML the holy grail of common data formats – or a form of software duct tape for sticking systems together? – Well, its ease of use and flexibility look life ensuring a long life – but its very flexibility can cause issues, with the diversity of schemas. However, as with COBOL, while it may not be the best approach in theory it is likely to be around for a long time yet.