CCS with Hennessy's Merge has no Finite Equational Axiomatization

  • Luca Aceto
  • Willem Jan Fokkink
  • Anna Ingólfsdóttir
  • Bas Luttik


This paper confirms a conjecture of Bergstra and Klop's from 1984 by establishing that the process algebra obtained by adding an auxiliary operator proposed by Hennessy in 1981 to the recursion free fragment of Milner's Calculus of Communicationg Systems is not finitely based modulo bisimulation equivalence. Thus Hennessy's merge cannot replace the left merge and communication merge operators proposed by Bergstra and Klop, at least if a finite axiomatization of parallel composition is desired.
How to Cite
Aceto, L., Fokkink, W., Ingólfsdóttir, A., & Luttik, B. (2003). CCS with Hennessy’s Merge has no Finite Equational Axiomatization. BRICS Report Series, 10(34).