The question of required elements has come up in discussion here. Specifically, among the top-level 19 elements (title, name, type of resource, etc.) none is mandatory. Nor do we propose that any among these be mandatory, but that leaves the possibility of empty records. An easy way out is to add the rule that "at least one of these 15 elements must occur". That would prevent empty records. But maybe it's reasonable to consider a rule like "at least one of 'title' and 'identifier' must occur". Is this a reasonable rule? While we don't think that 'title' (itself) should be mandatory, and neither do we think 'identifier' should (although we do recognize it is appropriate for an institution to develop metadata policies that might specify either of these as mandatory) if a record has neither title nor identifier, can it really identify anything? --Ray