Maybe it would be better to just have the value expressed in fractions, semihemidemisemihemidemisemiquaver seems untranslatable to me, More like a tongue twister than a term in use. But I'll try asking over there.
Some software also supports extremely short notes. 256th notes are easily accessible in Sibelius as of version 5, but some software supports even shorter notes. The shortest notated duration supported by Finale is a 4096th note, while LilyPond can write notes as short as a 1073741824th (2−30) note with up to 27 beams.