Update chapters/unitexpressions.tex

Co-authored-by: Henrik Tidefelt <henrikt@wolfram.com>

chapters/unitexpressions.tex

@@ -47,9 +47,12 @@ \section{The Syntax of Unit Expressions}\label{the-syntax-of-unit-expressions}
 
 The SI standard uses super-script for the exponentation, and does thus not define any operator symbol for exponentiation.
 A \lstinline[language=grammar]!unit-factor! consists of a \lstinline[language=grammar]!unit-operand! possibly suffixed by a possibly signed integer or rational number, which is interpreted as an exponent.
-Rational exponents are needed to fully support the unit for square roots (and can be used for roots in general).
-They are intended to be only be used when needed, i.e., not to represent integer exponents.
 There must be no spacing between the \lstinline[language=grammar]!unit-operand! and a possible \lstinline[language=grammar]!unit-exponent!.
+It is recommended to use the simplest representation of exponents, meaning that the explicit \lstinline!+! sign should be avoided, that leading zeros should be avoided, that rational exponents are reduced to not have common factors in the numerator and denominator, that rational exponents with denominator 1 should be avoided in favor of plain integer exponents, that the exponent 1 is omitted, and that entire factors with exponent 0 are omitted.
+
+\begin{nonnormative}
+Applications of rational exponents include units of square roots, units inferred from polynomial equations, and units of quantities used in certain modeling domains.
+\end{nonnormative}
 
 \begin{lstlisting}[language=grammar]
 unit-operand :