XHTML Modularization

XHTML modularization is a methodology for producing modularized markup languages in a number of different schema languages (currently DTDs, XML Schema and Relax NG) so that the modules can easily be plugged together to create markup languages.

Although it was originally designed to help manage the development of various XHTML Profiles, such as XHTML 1.1, XHTML Basic for mobile devices, and XHTML Print for sending to printers, the methodology is independent of XHTML, and has been used for the definition of other markup languages as well, such as SVG and MathML.

Read more about XHTML Modularization:  Method, Application To XHTML