August 10th, 2021
The MathML Core specification tries to address several issues related to implementing MathML in browsers. The MathML3 specification has been difficult to implement for browsers because it is big and does not contain very precise rules for rendering math formulas. MathML also has several parts that are not useful in browsers. The MathML Core specification tries to define an appropriate subset of MathML, describe its rendering in detail (using rules from the TeXBook and the Open Font Format as a basis), and clarify the interactions of MathML with other parts of HTML and the Open Web Platform.
The Math Working Group is also working on the rest of MathML. It is defining MathML4, the fourth version of MathML. The features included in MathML Core may evolve, or the second version of MathML Core may be defined, depending on how MathML4 develops.