origDate: @calendar (req) and one or more att.Datable attrs.

[mjhawkins]

Do we want this in GS?

The current implementation checks this entirely through schematron. A better solution would be to make calendar mandatory (perhaps even suggesting values - semi-closed list) via attDef. The schematron rule would then only have to ensure that one of the dating attrs exists.

If we are going to require the presence of at least one dating attr, we should include ALL of them in the list. In theory, you're only supposed to use the main ones when its the Gregorian calendar. If the date is from another calendar, we are supposed to use the '-custom' variant. In theory, we could enforce this, but I fear that it'd set off alarm bells in all of our collections.

[eifionjones]

we would have to retrospectively populate CUDL data with calendar attributes, but that would be fine