What is descobj and why is it there?

The descobject class:

<!ENTITY % local.descobj.class "">
<!ENTITY % descobj.class
		"abstract|authorblurb|epigraph
		%local.descobj.class;">

appears in component.mix, divcomponent.mix, and refcomponent.mix.
Why!? Does that make sense...

                                        Be seeing you,
                                          norm

-- 
Norman Walsh <>      | Look for the ridiculous in
http://www.oasis-open.org/docbook/ | everything and you will find
Chair, DocBook Technical Committee | it.--Jules Renard