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XMLWeb Design in a Nutshell, eMatter EditionChapter 25XMLCHAPTER 25
Introduction to XML
XML (Extensible Markup Language) is a new standard that has recently been
approved by the World Wide Web Consortium. It is a promising new customiz-
able markup language that will allow for complex information transactions on the
Internet. Many companies such as Microsoft and Netscape have developed or are
developing XML technologies.
HTML is designed for content being sent to a browser, but isn’t good for sending
content to other mediums like a printer or a ticker. XML allows developers to
create a custom markup language specific to their needs.
Specially coded XML documents reside on a server and can be converted to HTML
and read by browsers. Other clients (including future browsers that are XML-
compliant) can access the XML documents directly and use the content for a
variety of purposes.
Background
Although XML is a markup language like HTML, a common misconception is that
XML is HTML on steroids. XML and HTML are related, but through a common
parent, SGML, Standard General Markup Language. SGML is a meta-language—a
comprehensive set of syntax rules for marking up documents and data. For infor-
mation on SGML, including its history, see http://www.www.sil.org/sgml/, and
specifically,http://www.sil.org/sgml/general.html.#hist.
When the creators of the Web needed a markup language that told browsers how
to display web content, they used SGML guidelines to create HTML. HTML was
designed specifically for displaying content in a browser, but isn’t good for much
else.
Now that the Web has matured and we are using it for more than just viewing text
and images, we need to create more versatile markup languages. We could use
SGML as we did when creating HTML, but SGML wasn’t designed for the Web. It