It has come to our attention that there is an application here at LC that
would benefit from subcategories of subject, and I imagine this would have
fairly broad application. A lot of subject thesauri call these
"facets". In MARC we have a special field for faceted vocabularies
(654) and there is a subfield that contains a code for the facet, which is
defined by the particular vocabulary. Some examples of facets for the Art
and Architecture thesauri are: styles, activities, materials. There are
numerous other examples from some of our digital collections.

In MODS 3.1 we added this sort of thing under genre and
physicalDescription and called it "type". This was to accommodate
different aspects of genres (e.g. class, work, style) and of physical
forms (e.g. material, technique).  These are similar subcategories as we
are proposing for subject and perhaps these "type"s should be changed (in
the next major release) to "facet" as well.

We might want to add this attribute under both <subject> and <topic> (the
subelement under subject). That would allow some flexibility if different
topics within one subject string need to be subcategorized.

We are just finishing up a draft schema for version 3.2 which we will
announce shortly for review, and we thought we could add an attribute for
this sort of information now.

Would others have use for this?