For your consideration, a sutra on the definition of a sutra:
"alpaaksharam asandigdham saaravad vishvatomukham |
astobhyam anavadyam ca sUtram sUtra vido viduh ||"
"Minimal syllabary, unambiguous, pithy, addressing all that is pertinent,
non-redundant and without error, this is what those who know the sutra understand the sutra to be."
I think such a definition could be expanded to include any good writing.