Interface DocAttribute is a tagging interface which a printing attribute
class implements to indicate the attribute denotes a setting for a doc.
("Doc" is a short, easy-to-pronounce term that means "a piece of print
data.") The client may include a DocAttribute in a
attribute set to specify a characteristic of
that doc. If an attribute implements
PrintRequestAttribute as well as DocAttribute, the client may include the
attribute in a attribute set which specifies a print job
to specify a characteristic for all the docs in that job.