The following detail the changes made to the DTD in the 2001-09-03 DTD update. See also the change log.
The type attributes on question and questiongroup have been changed from a fixed list of values to CDATA to allow a more extensible list of values.
Elements name, date and address, corporatename and title have been added to the %data; parameter entity. These have been added to allow the identification of linkable/searchable terms in running text for electronic content.
The content model of title has been changed to allow more flexibility in the tagging of document titles. The new possibility also allows for the appearance of formulae and other data in document titles.