The evolution of CellML

CellML is an open XML-based markup language for describing and exchanging mathematical models of biological processes. While CellML was originally designed to describe and exchange models of cellular and subcellular processes, the design principles that were applied to the construction of a language with this relatively narrow focus are equally applicable to the specification of a language with a much wider scope. In this paper we describe the structure of CellML, how the language is evolving to broaden its scope, and what tools are being developed to facilitate its use.