24 research outputs found
Precongruence Formats with Lookahead through Modal Decomposition
Bloom, Fokkink & van Glabbeek (2004) presented a method to decompose formulas from Hennessy-Milner logic with regard to a structural operational semantics specification. A term in the corresponding process algebra satisfies a Hennessy-Milner formula if and only if its subterms satisfy certain formulas, obtained by decomposing the original formula. They used this decomposition method to derive congruence formats in the realm of structural operational semantics. In this paper it is shown how this framework can be extended to specifications that include bounded lookahead in their premises. This extension is used in the derivation of a congruence format for the partial trace preorder
On Characterising Distributability
We formalise a general concept of distributed systems as sequential
components interacting asynchronously. We define a corresponding class of Petri
nets, called LSGA nets, and precisely characterise those system specifications
which can be implemented as LSGA nets up to branching ST-bisimilarity with
explicit divergence.Comment: arXiv admin note: substantial text overlap with arXiv:1207.359
Axiomatizing Prefix Iteration with Silent Steps
Prefix iteration is a variation on the original binary version of the Kleene star operation P*Q, obtained by restricting the first argument to be an atomic action. The interaction of prefix iteration with silent steps is studied in the setting of Milner's basic CCS. Complete equational axiomatizations are given for four notions of behavioural congruence over basic CCS with prefix iteration, viz. branching congruence, eta-congruence, delay congruence and weak congruence. The completeness proofs for eta-, delay, and weak congruence are obtained by reduction to the completeness theorem for branching congruence. It is also argued that the use of the completeness result for branching congruence in obtaining the completeness result for weak congruence leads to a considerable simplification with respect to the only direct proof presented in the literature. The preliminaries and the completeness proofs focus on open terms, i.e. terms that may contain process variables. As a by-product, the omega-completeness of the axiomatizations is obtained as well as their completeness for closed terms. AMS Subject Classification (1991): 68Q10, 68Q40, 68Q55.CR Subject Classification (1991): D.3.1, F.1.2, F.3.2.Keywords and Phrases: Concurrency, process algebra, basic CCS, prefix iteration, branching bisimulation, eta-bisimulation, delay bisimulation, weak bisimulation, equational logic, complete axiomatizations
Nested Semantics over Finite Trees are Equationally Hard
This paper studies nested simulation and nested trace semantics over the language BCCSP, a basic formalism to express finite process behaviour. It is shown that none of these semantics affords finite (in)equational axiomatizations over BCCSP. In particular, for each of the nested semantics studied in this paper, the collection of sound, closed (in)equations over a singleton action set is not finitely based
Port Protocols for Deadlock-Freedom of Component Systems
In component-based development, approaches for property verification exist
that avoid building the global system behavior of the component model.
Typically, these approaches rely on the analysis of the local behavior of fixed
sized subsystems of components. In our approach, we want to avoid not only the
analysis of the global behavior but also of the local behaviors of the
components. Instead, we consider very small parts of the local behaviors called
port protocols that suffice to verify properties.Comment: In Proceedings ICE 2010, arXiv:1010.530
Robustness of Equations Under Operational Extensions
Sound behavioral equations on open terms may become unsound after
conservative extensions of the underlying operational semantics. Providing
criteria under which such equations are preserved is extremely useful; in
particular, it can avoid the need to repeat proofs when extending the specified
language.
This paper investigates preservation of sound equations for several notions
of bisimilarity on open terms: closed-instance (ci-)bisimilarity and
formal-hypothesis (fh-)bisimilarity, both due to Robert de Simone, and
hypothesis-preserving (hp-)bisimilarity, due to Arend Rensink. For both
fh-bisimilarity and hp-bisimilarity, we prove that arbitrary sound equations on
open terms are preserved by all disjoint extensions which do not add labels. We
also define slight variations of fh- and hp-bisimilarity such that all sound
equations are preserved by arbitrary disjoint extensions. Finally, we give two
sets of syntactic criteria (on equations, resp. operational extensions) and
prove each of them to be sufficient for preserving ci-bisimilarity.Comment: In Proceedings EXPRESS'10, arXiv:1011.601
Non-Deterministic Kleene Coalgebras
In this paper, we present a systematic way of deriving (1) languages of
(generalised) regular expressions, and (2) sound and complete axiomatizations
thereof, for a wide variety of systems. This generalizes both the results of
Kleene (on regular languages and deterministic finite automata) and Milner (on
regular behaviours and finite labelled transition systems), and includes many
other systems such as Mealy and Moore machines
Innocent strategies as presheaves and interactive equivalences for CCS
Seeking a general framework for reasoning about and comparing programming
languages, we derive a new view of Milner's CCS. We construct a category E of
plays, and a subcategory V of views. We argue that presheaves on V adequately
represent innocent strategies, in the sense of game semantics. We then equip
innocent strategies with a simple notion of interaction. This results in an
interpretation of CCS.
Based on this, we propose a notion of interactive equivalence for innocent
strategies, which is close in spirit to Beffara's interpretation of testing
equivalences in concurrency theory. In this framework we prove that the
analogues of fair and must testing equivalences coincide, while they differ in
the standard setting.Comment: In Proceedings ICE 2011, arXiv:1108.014
Query Nets: Interacting Workflow Modules that Ensure Global Termination
We address cross-organizational workflows, such as document workflows, which consist of multiple workflow modules each of which can interact with others by sending and receiving messages. Our goal is to guarantee that the global workflow network has properties such as termination while merely requiring properties that can be checked locally in individual modules. The resulting query nets are based on predicate/transition Petri nets and implement formal constructs for business rules, thereby ensuring such global termination. Our method does not require the notion of a global specification, as employed by Kindler, Martens and Reisig
Branching Time and Abstraction in Bisimulation Semantics
Abstract. In comparative concurrency semantics, one usually distinguishes between linear time and branching time semantic equivalences. Milner’s notion of ohsen~ation equirlalence is often mentioned as the standard example of a branching time equivalence. In this paper we investigate whether observation equivalence really does respect the branching structure of processes, and find that in the presence of the unobservable action 7 of CCS this is not the case. Therefore, the notion of branching hisimulation equivalence is introduced which strongly preserves the branching structure of processes, in the sense that it preserves computations together with the potentials in all intermediate states that are passed through, even if silent moves are involved. On closed KS-terms branching bisimulation congruence can be completely axioma-tized by the single axiom scheme: a.(7.(y + z) + y) = a.(y + z) (where a ranges over all actions) and the usual laws for strong congruence. WC also establish that for sequential processes observation equivalence is not preserved under refinement of actions, whereas branching bisimulation is. For a large class of processes, it turns out that branching bisimulation and observation equivalence are the same. As far as we know, all protocols that have been verified in the setting of observation equivalence happen to fit in this class, and hence are also valid in the stronger setting of branching hisimulation equivalence