We need an attribute such as @rational (or @alt or @fraction aut sim.) for when the normalized numeric value of the number being encoded is better represented in some form other than a pure decimal number as imposed by data.numeric. This might include non-simple fractions (1/3 or 5/12), where the ratio itself is of more interest than the decimal value rounded to some number of significant figures.
<num value="0.042">κδ</num> (where _kd_ is the ancient Greek for 24 or in this case 1/24)
<num rational="1/24">... (would give more useful information for both searching and for analysis of numeric patterns in manuscript)