I've also been trying to use the <endDate>OPEN</endDate> under termOfGrant
as suggested by the PREMIS Data Dictionary
"Use “OPEN” for an open ended term of grant. Omit endDate if the
ending date is unknown or the permission statement applies to many
objects with different end dates" but it doesn't validate. I take it that
this is due to the schema wanting a numeric value. Should I therefore be
using 9999 as seen in other examples?