Trace Semantics for Coalgebras

  • Authors:
  • Bart Jacobs

  • Affiliations:
  • Department of Computer Science, University of Nijmegen, P.O. Box 9010, 6500 GL Nijmegen, The Netherlands

  • Venue:
  • Electronic Notes in Theoretical Computer Science (ENTCS)
  • Year:
  • 2004

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Abstract

Traditionally, traces are the sequences of labels associated with paths in transition systems X-P(AxX). Here we describe traces more generally, for coalgebras of the form X-P(F(X)), where F is a polynomial functor. The main result states that F's final coalgebra Z-@?F(Z) gives rise to a weakly final coalgebra with state space P(Z), in a suitable category of coalgebras. Weak finality means that there is a coalgebra map X-P(Z), but there is no uniqueness. We show that there is a canonical choice among these maps X-P(Z), namely the largest one, describing the traces in a suitably abstract formulation. A crucial technical ingredient in our construction is a general distributive law FP@?PF, obtained via relation lifting.