Reversible enhanced event structures: Towards reversible E-LOTOS

After studying how undoing of events of irreversibly aging processes complicates in the presence of urgent events or occasionally suspended subprocesses, we propose a reversibility operator for the standard process-algebraic specification language E-LOTOS, whose recently proposed true-concurrency semantics is based on enhanced event structures (EESs). With this operator, the reversibility of events executed by a real-time process and the urgency of their undoing can be specified with respect to their external appearance and the time elapsed since their execution. To facilitate definition of the operator, we introduce a very fine control of event undoing into the general EESs.