vienna definition language

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

Vienna Definition Language
VDL

   (VDL) IBM Vienna Labs.  A language for formal, algebraic
   definition via operational semantics.  Used to specify the
   semantics of PL/I.  See also {VDM}.

   ["The Vienna Definition Language", P. Wegner, ACM Comp Surveys
   4(1):5-63 (Mar 1972)].