Welcome to the OpenMath website. OpenMath is an extensible standard for representing the semantics of mathematical objects. If you haven't heard about it before you might want to consult the overview.
T. Gruber, and G. Olsen. Principles of Knowledge Representation and Reasoning: Proceedings of the 4th International Conference (KR '94): Bonn, Germany: 1994, May, 24 - 27, page 258-269. Morgan Kaufmann Publishers, (1994)