Technical Report

Real-time systems are normally divided into two classes: Hard and Soft. The dierence lies in how critical it is to meet the systems timing constraints. In a hard real-time system, every deadline must be met. If not, the consequences to the environment is above an accepted level. On account of this, the Worst Case Execution Time is in focus for a number of proposed approaches. A soft real-time system, on the other hand, is characterized by the fact that a missed deadline do not cause system failure and do not cause damage to the environment. This is most likaly the reason why timing constraints in soft real-time systems are handled by dierent ad hoc solutions. (E.g. Do not write more than k lines of code in one block.) But even if a missed deadline is not directly dangerous, the consequences may indirectly be serious