Limiting dramatically increases performance and usability by preventing extraneous parsing.
<choice>, <list>, and <freetext> can be limited. If one output from
the element parses to completion, no further outputs will parse.
In general, limits should be applied agressively. Insufficiently-limited grammars are very slow to parse and result in many unneeded output options for the user to deal with.
For a <choice>, the outputs are attempted in the order they appear in the
grammar.
For a <list>, the outputs are attempted based upon the score that comes
from parsing each item.
For a <freetext>, the outputs are attempted based based upon the greedy
prop - shortest-to-longest by default, or longest-to-shortest if greedy is
true.