Paragraph about Scientific software
Even within the SGML framework, one can consider various levels of verbosity (I am grateful to Neil Soiffer for offering these examples), depending on how much information you encode in the leaves (CDATA) Scientific software of the SGML tree, and how much you encode in the SGML structure itself. Consider the expression 2x+y, which might be encoded as
[MATH] [MROW] [MROW] [MN] 2 [/MN] [MO] ⁢ [/MO] [MI] x [/MI] [/MROW] [MO] + [/MO] [MI] y [/MI] [/MROW] [/MATH]Where MI means Math Identifier, MO means Math Operator, and we have used  to enclose the SGML markers. By mathlab contrast, extended MathML with a parser that knows some precedence rules could have a simpler SGML:
[MATH] 2 ⁢ x + y [/MATH]The tradeoff is that the first version might allow standard SGML to validate, search, index (or whatever) the math expressions. The second version requires some external parser that knows about precedence (etc), but is easier for a human to comprehend and write, and simpler to transmit (and probably to store). There are intermediate choices as well.