contains the physical form of the document, i.e. single sheet, libellum, rotulus ...
General Comment: The <form> element may often contain only a single word or phrase: at a later revision of this standard, it is possible that it will be supplied as an attribute value
let us say Physical form, because this might be confused with documentary form. But, would not this description be under medium?
(Luciana Duranti, 2007-02-18 13:09:50)