Document Structure Definition (DSD) is a newly
announced schema language for XML documents
produced
as a result of collaborative research between AT&T
and
BRICS University
in Denmark.
DSD is able to express conditional constraints,
ordered and unordered content types and other
features
beyond the power of DTDs. It also provides a CSS
style mechanism for inserting default elements and
attributes, and as such is different from the W3C Schema language which
is currently a Working Draft.
The DSD language is already fully implemented and
is open source. More information is available from
the
DSD
website.