     The requirements stage of software development is key to a project's     success, especially with respect to safety.  For that reason,      my colleagues and I have concentrated on requirements, especially     the communication of requirements via a requirements specification.     To that end we have developed a state-based language called     <A HREF="http://www.cs.washington.edu/research/projects/safety/www/papers/rsml-grammar/rsml-grammar.html">     <EM>Requirements State Machine Language</EM></A>, or RSML.     We have validated the usefulness of this language by     specifying <A HREF="http://www.cs.washington.edu/homes/jdreese/TCAS-II-Description.htm">TCAS II</A>,      an avionics system.  <P>
