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Lecture Notes in Computer Science
In order to model concurrency, we extend automata theory from the usual word languages (sets of labelled linear orders) to sets of labelled series-parallel posets | or, equivalently, to sets of terms in an algebra with two product operations: sequential and parallel. We rst consider languages of posets having bounded width, and characterize them using depth-nilpotent algebras. Next we introduce series-rational expressions, a natural generalization of the usual rational expressions, as well as adoi:10.1007/bfb0028590 fatcat:76pd54rcvvanldopkvpx54pcii