XML is a standard that is designed to encode information in a structured and accessible manner. It is a stable and reliable standard, vendor-independent and managed by the World Wide Web Consortium (W3C) and supported by a wide range of application and system vendors. A number of related standards, each using the core XML standard itself, have also been developed to respond to the specific demands of information management.
Some of these additional standards have been criticized for their apparent complexity and for creating a potentially tangled web of dependencies that might make their deployment less effective or less straightforward. This overlooks the fact that it is in the ‘genetic’ makeup of XML to be evolutionary, and even more standards are likely to emerge. As with DNA, the complexity of an XML standard or an XML document that uses it is proportional to the complexity of the ‘organism’ or the task for which it has been designed. For simple tasks and simple document structures, XML can be deployed in a simple manner – this is the principle of extensibility that we find in the standard’s name.
To understand the anatomy of XML, we will look at an analogy using natural human language. A single alphabet or character set can underpin a range of languages. This is important of course to keyboard manufacturers, typeface copyright holders and anyone involved in displaying information to an end user. A character set on its own, however, does not constitute a language, any more than being able to recognize individual letters constitutes an ability to understand a language that uses the character set.