Hi Michael,
according to the DTD a grace note does not have a duration, but also it is not required to have a type-tag.
Indeed I stumbled over a dolet-created sibelius-export with graces-notes not having either of both.
PriMus crashed because of an undefined note-value.
That does not make sense to me. A grace note should have a nominal duration, at least expressed by a type tag, shoudn't it?
Christof