Why Two Different Kinds of Markup?
Chapters 3 and 4 describe two kinds of markup for encoding mathematical material in documents: Presentation markup captures notational structure. It encodes notational structure in a sufficiently abstract way to facilitate rendering to various media. Thus, the same presentation markup can be rendered with relative ease on screen in either wide and narrow windows, in ASCII or graphics, in print, or it can be enunciated in a sensible way when spoken. It does this by providing information such as grouping of expression parts, classification of symbols, etc. Presentation markup does not directly concern itself with the mathematical structure or meaning of an expression. In many situations, notational structure and mathematical structure are closely related, so a sophisticated processing application may be able to heuristically infer mathematical meaning from notational structure. However, in practice, the inference of mathematical meaning from mathematical notation must often be left to th
