The Free On-line Dictionary of Computing (30 December 2018):

RAISE Specification Language
RSL

    (RSL) (RAISE = Rigorous Approach to Industrial
   Software Engineering).  A wide-spectrum specification and
   design language developed by ESPRIT Project 315 at CRI
   A/S, Denmark.  Systems may be modular, concurrent and
   nondeterministic.  Specifications may be applicative or
   imperative, explicit or implicit, abstract or concrete.

   ["The RAISE Specification Language", RAISE Language Group, P-H
   1992, ISBN 0-13-752833-7].

   (2007-10-02)