MATHML

Mathematical Markup Language, or MathML, is an XML application for describing mathematical notation and capturing both its structure and content. The goal of MathML is to enable mathematics to be served, received, and processed on the Web, just as HTML has enabled this functionality for text. The challenge in putting math on the Web is to capture both notation and content in such a way that documents can utilize the highly-evolved notational practices of print, and the potential for interconnectivity in electronic media.

http://www.idealliance.org/XMLRoadmap/WEB/ts0/tp15.htm