WSML: Website Markup Language
WSML is a simple extension to xhtml that allows to populate directories of web sites with coordinated web pages that share a menu, and a logo (typically on the left panel). Individual pages differ in the page heading and the page content.
The top-level element is a <ws:website> element. It contains an optional <ws:up> element that specifies the link to the parent directory followed by a list of <ws:page>, <ws:folder>, <ws:pageref> elements. The former are used to specify originary content on the content panel (see below), <ws:pageref> and <ws:folder> create links to external pages and subdirectories in the menu panel.
The <ws:page> element is used to specify a content panel of a page. It's name attribute specifies the name of the generated html file. The element contains a <ws:pagetitle> element for representing the page title, a <ws:menu> element for specifying the link text for this page in the menu panel, and XHTML <head> and <body> elements that are copied into the generate html file.
To find out more about WSML consider the examples on this web site and read the RelaxNG schema for WSML (ws.rnc). The generation of the html pages is done by the ws2html.xsl style sheet.