PrintRequestAttribute is a tagging interface which a
printing attribute class implements to indicate the attribute denotes a
requested setting for a print job.
Attributes which are tagged with PrintRequestAttribute and are also
tagged as PrintJobAttribute, represent the subset of job attributes
which can be part of the specification of a job request.
If an attribute implements DocAttribute as well as
PrintRequestAttribute, the client may include the attribute in a
Doc's attribute set to specify a job setting which pertains just to
that doc.
DocAttributeSet, PrintRequestAttributeSet