DSSSL

from The Free On-line Dictionary of Computing (8 July 2008)

Document Style Semantics and Specification Language
DSSSL

   (DSSSL) An {ISO} {standard} under preparation, addressing the
   {semantics} of high-quality composition in a manner
   independent of particular formatting systems or processes.
   DSSSL is intended as a complementary standard to {SGML} for
   the specification of semantics.

from V.E.R.A. -- Virtual Entity of Relevant Acronyms (June 2006)

DSSSL
       [standard] Document Style Semantics and Specification Language
(DTD, ISO, IEC, DIS 10179)