  Safety-Critical Java (SCJ) is a recent technology that restricts the
execution and memory model of Java in such a way that applications can be
statically analysed and certified for their real-time properties and safe use
of memory. Our interest is in the development of comprehensive and sound
techniques for the formal specification, refinement, design, and implementation
of SCJ programs, using a correct-by-construction approach. As part of this
work, we present here an account of laws and patterns that are of general use
for the refinement of SCJ mission specifications into designs of parallel
handlers used in the SCJ programming paradigm. Our notation is a combination of
languages from the Circus family, supporting state-rich reactive models with
the addition of class objects and real-time properties. Our work is a first
step to elicit laws of programming for SCJ and fits into a refinement strategy
that we have developed previously to derive SCJ programs.
