In this paper we describe a language for defining scheduling
algorithms for hard real-time systems and a tool to simulate the
behavior of such systems on a predefined task set. The language is
suited for describing a real-time system composed of a task set,
resources and a scheduling algorithm. The tasks can either be periodic
or aperiodic, dependent or independent and the time constraints
(e.g. deadlines) may be soft or hard. We consider two types of
resources: the cpu and semaphores. Semaphores are used to describe
the various possible dependences of the task set: shared memory,
inter-task communication, devices,... We consider only mono-processor
real-time systems. The third part of the system is given by the
scheduling algorithm which is used to give resources (cpu and
semaphores) to tasks.