A string indicating what the date refers to. The value of role should be taken from the vocabulary maintained at http://www.ivoa.net/rdf/voresource/date_role. This includes the traditional and deprecated strings “creation”, indicating the date that the resource itself was created, and “update”, indicating when the resource was updated last, and the default value, “representative”, meaning the date is a rough representation of the time coverage of the resource. The preferred terms from that vocabulary are the DataCite Metadata terms. It is expected that the vocabulary will be kept synchronous with the corresponding list of terms in the DataCite Metadata schema. Note that this date refers to the resource; dates describing the metadata description of the resource are handled by the “created” and “updated” attributes of the Resource element.