Thayer Watkins
Silicon Valley
& Tornado Alley

The Extensible Markup Language

The Extensible Markup Language XML is an application of SGML, Standard Generalized Markup Language. HTML is also an application of SGML. However XML, rather than being another markup language, is a language for creating specialized markup language. And XML allows the creation of languages that are more than markup languages. It allows the specification of the information content of documents to facilitate data transfer as for databases.

XML is the creation of a subgroup of the World Wide Web Consortium (W3C). XML, like HTML, functions through the use of tags. But the W3C saw fit to require the languages created with XML satisfy several requirements that differ from HTML. These are:

XHTML is a reformulation of HTML which complies with the requirements of XML. An HTML file edited to comply with XHTML has the advantage that it is better structured for search engines and it can be delivered by more internet media types such as palm computers. An XHTML does require the change of the initial lines of codes of the HTML file. The first line of an XHTML 1.0 file must be of the form:

<?xml> version="1.0" encoding="UTF-8"?>

The document type tag for XHTML should be:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHYML 1.0 Strict"//EN" "">

The HTML tag also must be expanded to the form:

<html xmlns="" xml:lang="en" lang="en">

There are many powerful markup languages which have been created with XML. Among them are the following: