CCS expressions finite state processes, and three problems of equivalence
Information and Computation
Communicating and mobile systems: the &pgr;-calculus
Communicating and mobile systems: the &pgr;-calculus
Proof, language, and interaction
Communication and Concurrency
PI-Calculus: A Theory of Mobile Processes
PI-Calculus: A Theory of Mobile Processes
On the expressive power of temporal concurrent constraint programming languages
Proceedings of the 4th ACM SIGPLAN international conference on Principles and practice of declarative programming
Regular Expressions in Process Algebra
LICS '05 Proceedings of the 20th Annual IEEE Symposium on Logic in Computer Science
Computation: finite and infinite machines
Computation: finite and infinite machines
Replication vs. recursive definitions in channel based calculi
ICALP'03 Proceedings of the 30th international conference on Automata, languages and programming
Recursion versus replication in simple cryptographic protocols
SOFSEM'05 Proceedings of the 31st international conference on Theory and Practice of Computer Science
On the Expressive Power of Restriction and Priorities in CCS with Replication
FOSSACS '09 Proceedings of the 12th International Conference on Foundations of Software Science and Computational Structures: Held as Part of the Joint European Conferences on Theory and Practice of Software, ETAPS 2009
The decidability of the reachability problem for CCS!
CONCUR'11 Proceedings of the 22nd international conference on Concurrency theory
Decidability of behavioral equivalences in process calculi with name scoping
FSEN'11 Proceedings of the 4th IPM international conference on Fundamentals of Software Engineering
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A remarkable result in [4] shows that in spite of its being less expressive than CCS w.r.t. weak bisimilarity, CCS! (a CCS variant where infinite behavior is specified by using replication rather than recursion) is Turing powerful. This is done by encoding Random Access Machines (RAM) in CCS!. The encoding is said to be non-faithful because it may move from a state which can lead to termination into a divergent one which do not correspond to any configuration of the encoded RAM. I.e., the encoding is not termination preserving. In this paper we study the existence of faithful encodings into CCS! of models of computability strictly less expressive than Turing Machines. Namely, grammars of Types 1 (Context Sensitive Languages), 2 (Context Free Languages) and 3 (Regular Languages) in the Chomsky Hierarchy. We provide faithful encodings of Type 3 grammars. We show that it is impossible to provide a faithful encoding of Type 2 grammars and that termination-preserving CCS! processes can generate languages which are not Type 2. We finally show that the languages generated by termination-preserving CCS! processes are Type 1.