howto: handle temporal visibility of a document?

[Clemens Wyss DEV]

We have documents that are not always visible (visiblefrom-visibleto). In order 
to not have to query the originating object of the document whether it is 
currently visible (after the query), we'd like to put metadata into the 
documents, so that the visibility can be determined at query-time (by the query 
itself or a query filter). Any suggestions on how to index and query this 
metadata?