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On Fri, Jun 16, 2006 at 01:42:55PM -0400, Priscilla Caplan wrote: > In (rights) permissionStatement.termOfGrant the start and end date of > the permission granted is required and ISO 8601 format is recommended. > But what if something has no real start (e.g. fair use) or no end > (e.g. perpetual)? > > Seems like you wouldn't want to say "none" because that wouldn't pass > parsing. Perhaps you could use "0000" for no start date and "9999" for > no end date -- this seems to be what is done in the PREMIS examples. > > Is there a standard convention that people use? my favorite starting point for these sorts of questions is john kunze's A Metadata Kernel for Electronic Permanence (5 October 2001); it's the most complete treatment of this topic i know. it defines the following "Missing value codes and their meanings." now, it doesn't specifically say that these values should be used for dates, but since the Electronic Resource Citation (ERC) being discussed includes "when" as a core data element, i imagine they could be used there (though some of them will not be applicable to dates, for obvious reasons). (:unkn) unknown (e.g., Anonymous, Inconnue) (:unav) value unavailable indefinitely (:unac) temporarily inaccessible (:unap) not applicable, makes no sense (:unas) value unassigned (e.g., Untitled) (:none) never had a value, never will (:null) explicitly empty (:unal) unallowed, suppressed intentionally (:tba) to be assigned or announced later i believe the use of "0000" for an unspecified date is illegal; see http://www.w3.org/TR/xmlschema-2/#dateTime, sec. 3.2.7, last paragraph before Note.