Operational semantics of rewriting with priorities

We study the semantics of term rewriting systems with rule priorities (PRS), as introduced in Baeten et al. (1989). Three open problems posed in that paper are solved, by giving counter examples. Moreover, a class of executable PRSs is identified. A translation of PRSs into transition system specifications (TSS) is given. This translation introduces negative premises. We prove that the translation preserves the operational semantics