The MathML domain elements enable direct use of MathML markup within DITA documents, as well as use-by-reference of MathML markup that is stored separate, non-DITA documents. MathML is a W3C standard.
For MathML markup that is stored directly in DITA documents that are validated using DTDs, the MathML elements must use a namespace prefix in order to avoid conflict with the DITA-defined elements of the same name. Documents validated using XSD or RELAX NG can default the MathML namespace on the MathML math element. MathML elements that are referenced using the mathmlref element do not need to have a namespace prefix, because they are parsed separately from the DITA documents that refer to them. By default, the MathML domain is configured to use the namespace prefix "m" for the MathML elements.