%mml-product.class;
MathML-3.0-only Product Class Element
Class redefined in the MathML 3.0 setup modules to prevent collision between MathML 3.0 and JATS. Both JATS and MathML 3.0 (but not MathML 2.0) contain a <product> element, and both JATS and MathML 3.0 named a parameter entity “product.class”.
Remarks
When MathML 2.0 became MathML 3.0, the parameter entity
“product.class” was defined by both the MathML 3.0 DTD and the JATS-default-classes.ent module. JATS (after discussion with the W3C MathML Committee) has renamed the class in the MathML DTD. The new MathML 3.0 parameter entity is called “mml-product.class”, and JATS retains its parameter entity “product.class” with a different meaning.