What is XML and its relevance to CML?
XML (eXtensible Markup Language) has been developed by a large and dynamic group under the aegis of the W3 consortium. It’s essentially a subset (or simplification) of SGML and is much easier to use. If you know how to write valid HTML it’s a very small step to using XML. In fact, if you are already familiar with the latest specifications for HTML known as XHTML (http://www.w3.org/MarkUp/), you are already using XML! The main features of XML are: • Easy to use, both authoring and reading • No complex supporting documents • XML documents need not be valid and can simply be well-formed • Universal acceptance • Simple to write parsing software Well-formed is an important new concept. It means that a document is syntactically correct (e.g. the start and end tags balance, attribute values are quoted, etc.) even if it might not be valid (e.g. contain an unknown tag). XML is therefore very well suited to situations where the documents have already been validated (e.g. because the authoring so
