RE: Akoma Ntoso as a working /in-progress document

This question is coming from the discussion in the last tc-meeting.
There was a question raised by Grant (and also I believe Veronique) on
working documents - where all the information may not be available
during some stages of markup (e.g. dateTime period information ) -
some of these are mandatory for the document to be valid. The
conclusion appeared to be that the schema has to accommodate an
unknownDateTime / unknownPeriod attribute setting for such cases ( I
lost the connection towards the end - so i am not sure if there was
further discussion on this ) .    I would also think there are other
use cases of this type which we don't know about yet - what is the
recommended practice in such cases - do we leave the working document
invalid until such information is available  ?