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Topic: Bisimulation

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	Bisimulation - Wikipedia, the free encyclopedia
		In theoretical computer science a bisimulation is an equivalence relation between state transition systems, associating systems which behave in the same way in the sense that one system simulates the other and vice-versa.
		Since Kripke models are a special case of (labelled) state transition systems, bisimulation is also a topic in modal logic.
		In fact, modal logic is the fragment of first-order logic closed under bisimulation (Van Benthem's theorem).
	en.wikipedia.org /wiki/Bisimulation (417 words)

	Pi-calculus - Wikipedia, the free encyclopedia
		This can be seen by the fact the bisimulation equivalence becomes decidable for the recursion-free calculus and even for the finite-control π-calculus where the number of parallel components in any process is bounded by a constant (Mads Dam: On the Decidability of Process Equivalences for the pi-Calculus.
		In the π-calculus, the definition of bisimulation equivalence (aka bisimilarity) may be based on either the reduction semantics or on the labelled transition semantics.
		The reader should note that, in the literature, the term open bisimulation usually refers to a more sophisticated notion, where processes and relations are indexed by distinction relations; details are in Sangiorgi's paper cited above.
	en.wikipedia.org /wiki/Pi-calculus (2290 words)

	Henzinger/Rajamani: Fair Bisimulation (Site not responding. Last check: 2007-10-31)
		Indeed, the definitions of fair bisimulation that have been proposed in the literature sacrifice locality, and with it, also efficient checkability.
		In each step of the infinite bisimulation game, the adversary chooses one system, makes a move, and the protagonist matches it with a move of the other system.
		Consistent with this game-based view, we call two fair transition systems bisimilar if in the bisimulation game, the infinite path produced in the first system is fair iff the infinite path produced in the second system is fair.
	www-cad.eecs.berkeley.edu /~tah/Publications/fair_bisimulation.html (309 words)

	LICS 2001 (Site not responding. Last check: 2007-10-31)
		In this paper, we relate the expressiveness of levels of the fixpoint alternation depth hierarchy of the mu-calculus (the mu-calculus hierarchy) with the expressiveness of the bisimulation invariant fragment of levels of the monadic quantifiers alternation-depth hierarchy (the monadic hierarchy).
		polymodal Logic) is as expressive as the bisimulation invariant fragment of monadic Sigma_0 (i.e.
		the nu\mu-level) of the mu-calculus hierarchy is as expressive as the bisimulation invariant fragment of monadic Sigma_1 (resp.
	www.labri.fr /Perso/~janin/Rech/lics01.html (180 words)

	Bisimulation (Site not responding. Last check: 2007-10-31)
		Equivalently R is a bisimulation if for every pair of elements p, q in S, if (p,q)is in R then for all α in Λ, andfor all p' in S, implies that there is a q' in S such that
		For p and q to bebisimilar, the simulation between p and q must be the inverse of thesimulation between q and p.
		Typically, if the state transition system givesthe operational semantics of a programming language, thenthe precise definition of bisimulation will be specific to the rstrictions of the programming language.
	www.therfcc.org /bisimulation-80711.html (355 words)

	EXPRESS'98: Accepted Papers (Site not responding. Last check: 2007-10-31)
		We exhibit a closed term that has a deadlock in split semantics, but not in ST bisimulation semantics, and vice versa: a closed term that has a deadlock in ST bisimulation semantics but not in split semantics.
		It is coarser than probabilistic bisimulation, yet non-probabilistic branching-time, and differs from probabilistic equivalences developed for CSP \cite{lo:low2,mo:ms,se:sei}.
		This restriction, for computable data with a built-in equality predicate, yields a less expressive formalism, namely equality in the strong bisimulation algebra coincides with the universal fragment of first-order logic for the data; so the input prefix mechanism gives rise to strong bisimulation algebras for which equality is complete in $\Pi^0_1$.
	www.cse.psu.edu /~catuscia/EXPRESS98/accepted.html (1212 words)

	Bisimulation relations for dynamical, control, and hybrid systems
		The fundamental notion of bisimulation equivalence for concurrent processes, has escaped the world of continuous, and subsequently, hybrid systems.
		We prove that this notion can be captured by the abstract notion of bisimulation as developed by Joyal, Nielsen and Winskel.
		Furthermore, this enables the development of a novel and natural notion of bisimulation for hybrid systems, which is the final goal of this paper.
	repository.upenn.edu /ese_papers/171 (171 words)

	Natalia López's Publications: Concurrency (Site not responding. Last check: 2007-10-31)
		Bisimulations are a broadly used formalism to define the semantics of process algebras.
		In particular, by means of weak bisimulation most of the internal activity of processes may be abstracted.
		Global timed bisimulation is defined exactly as weak timed bisimulation once ordinary transitions are replaced by the adequate notions of generalized transitions.
	dalila.sip.ucm.es /~natalia/publi.html (557 words)

	A Coalgebraic Theory of Sequences in PVS
		Bisimulation, invariant, simulation (for prefix order on sequences), and admissability proof methods are developed based on the uniqueness property.
		The main advantage of this coinductive approach is that it allows us to deal with sequences in a step-by-step manner: we always define and prove by looking at the next step in a sequence.
		A relation is a bisimulation if it is closed under application of the destructor of a coalgebra.
	www.cs.kun.nl /~bart/sequences.html (774 words)

	Simulation
		Johan van Benthem, etc., etc., etc.: by the late 1980s, development of simulation and bisimulation games had become a cottage industry.
		For example, in the Barwise-Immerman bisimulation game, all equivalence classes are FO + LFP expressible, while the equivalence relation preserves FO + PFP queries.
		This view of bisimulation games is developed further in my paper on Pebble Games and...
	www.math.usf.edu /~mccolm/RGbisimulation.html (708 words)

	applicative bisimulation (Site not responding. Last check: 2007-10-31)
		I use Howe's method from LICS'89 to show that applicative bisimulation is a congruence, and then prove the validity of a collection of equational properties of applicative bisimulation.
		We study two senses of operational equivalence, one of which is a form of Abramsky's applicative bisimulation, and show them to be congruences.
		We prove equational laws that are analogous to the axiomatic domain theory of LCF and derive a co-induction principle.
	www.cis.upenn.edu /~bcpierce/types/archives/1993/msg00111.html (514 words)

	Process Algebra: Open Problems and Future Directions
		While Markovian bisimulation induces an exact aggregation at the Markov chain level (ordinary lumping), it is not known what happens with Markovian testing.
		Weak bisimulation equivalence is an example of a semantic equivalence that respects such traces: two weakly bisimilar processes always have the same deadlock/livelock traces.
		In contrast, there exists a finite equational axiomatisation of strong bisimulation equivalence on recursion-free CCS using two auxiliary binary operators, namely the left merge and the communication merge of ACP.
	www.cs.auc.dk /~luca/BICI/open-problems.html (1145 words)

	Bisimulation Equivalence and Divergence in CCS (Site not responding. Last check: 2007-10-31)
		Abstract: By introducing `convergence predicates' on the set of terms of the language of CCS, behavioural preorders based upon the idea of bisimulation but refining the notion of bisimulation equivalence and incorporating explicit treatments of `divergence' are defined.
		The associated precongruence relations are characterized and complete axiomatizations of these relations for the sets of closed finite terms and regular expressions are presented.
		A revised version of this report was published as ``Bisimulation and Divergence'' in Information and Computation, 85 (2) 1990, pp.202--241.
	www.lfcs.informatics.ed.ac.uk /reports/87/ECS-LFCS-87-29/index.html (82 words)

	Process calcululi for web services
		Bisimulation is a way to judge whether two programs (or specifications) are equivalent.
		You can partly fix this problem within bisimulation: by only comparing on those actions that are mentioned in the specification.
		This book is the definitive tome on all the hundreds of different possible bisimulations, and on how they relate, and on congruences.
	www.wischik.com /lu/research/choreography.html (1165 words)

	A Process Algebra Diary (Site not responding. Last check: 2007-10-31)
		I may be the only dinosaur left treading this planet, but I am still fascinated by the study of equational characterizations of the parallel composition operation modulo (variations on) the classic notion of bisimulation equivalence.
		In particular, I am spending some time on the study of axiomatizations for parallel composition that use auxiliary operators, aiming at showing that the left and communication merge operators of Bergstra and Klop have somehow a canonical status in the finite equational axiomatization of parallel composition.
		This is due to the fact that, in strong bisimulation semantics, no finite collection of equations can express the interplay between interleaving and communication that underlies the semantics of Hennessy's merge.
	www.cs.aau.dk /~luca/PA-DIARY/16-03-2004.html (408 words)

	Theory Mini-Course 2000-01 (Site not responding. Last check: 2007-10-31)
		The first lecture should be very accessible and give a gentle introduction to the advantages of viewing models for concurrency as categories, in which the arrows are forms of simulation.
		The lecture will be mainly based on the familiar model of labelled transition systems, but will indicate how the ideas are equally applicable to other models such as event structures and Petri nets, and how relations between different models are often expressed as adjunctions.
		Bisimulation between presheaves is again obtained from open maps.
	www.cl.cam.ac.uk /~mpf23/Mini-courses/2000-01/Winskel.html (444 words)

	Branching Time and Abstraction in Bisimulation Semantics
		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 t of CCS this is not the case.
		Therefore the notion of branching bisimulation 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.
		For a large class of processes it turns out that branching bisimulation and observation equivalence are the same.
	theory.stanford.edu /~rvg/abstraction/abstraction.html (508 words)

	Weak Bisimulation and Open Maps (Site not responding. Last check: 2007-10-31)
		A systematic treatment of weak bisimulation and observational congruence on presheaf models is presented.
		A general notion of weak open-map bisimulation is introduced, and results relating various notions of strong and weak bisimulation are provided.
		The abstract theory is accompanied by the concrete study of two key models for concurrency, the interleaving model of synchronisation trees and the independence model of labelled event structures.
	www.brics.dk /~luca/weabom.html (205 words)

	MADOC - Über abstrakte Charakterisierungen von Bisimulation
		Bisimulation wurde von Milner (1980) und Park (1981) auf Transitionssystemen eingefuehrt, um Prozesse zu identifizieren, die aus Sicht eines externen Beobachters nicht zu unterscheiden sind.
		Bisimulation was introduced by Milner (1980) and Park (1981) in order to identify processes that cannot be distinguished by an external agent.
		Further on it gives a new perspective on the phenomen "bisimulation": While Milner introduces bisimulation as a relation which he interprets as "a kind of invariant holding between a pair of dynamic systems", AM-bisimulation itself is a dynamic system.
	bibserv7.bib.uni-mannheim.de /madoc/volltexte/1999/10/index.html (491 words)

	There are practical applications in which weak bisimulation poses a problem that can be solved by moving to branching ... (Site not responding. Last check: 2007-10-31)
		On the other hand we are not aware of a single application where weak bisimulation semantics can be successfully applied, but the extra distinctions made in branching bisimulation semantics pose a problem.
		In branching bisimulation semantics this yields a process with 17 states, whereas in weak bisimulation semantics a process with only 14 states is obtained.
		However, whenever weak bisimulation performs better than branching bisimulation, it turns out to be the case that neither of the two notions are really suitable, and coupled simulation, or an even coarser equivalence, is called for.
	theory.stanford.edu /people/rvg/abstraction/node16.html (407 words)

	Branching bisimulation equivalence is the only known equivalence in the linear time - branching time spectrum that ...
		Branching bisimulation equivalence is the only known equivalence in the linear time - branching time spectrum that supports an `eventually' operator as part of a temporal logic on transition systems.
		As mentioned in the introduction, weak bisimulation semantics is not adequate for a modal logic with eventually operator.
		In DE NICOLA and VAANDRAGER (1990a) branching bisimulation, after being translated to Kripke structures, is shown to coincide with stuttering equivalence.
	theory.stanford.edu /people/rvg/abstraction/node15.html (432 words)

	Up-to Techniques for Weak Bisimulation
		While up-to techniques for strong bisimilarity are well understood, in the weak case they come as a collection of unrelated results, and lack a unified presentation.
		We propose a uniform and modular theory of up-to techniques for weak bisimulation that captures existing proof technology and introduces new techniques.
		We also define a theory of up-to techniques for elaboration that in particular validates an elaboration up to elaboration technique, while it is known that weak bisimulation up to weak bisimilarity is unsound.
	perso.ens-lyon.fr /damien.pous/upto (431 words)

	UMCS-96-1-1 Modal Observation Equivalence of Processes (Site not responding. Last check: 2007-10-31)
		Strong bisimulation equivalence was shown by Milner to be characterised in this way.
		The paper constructs a template which can be used to generate a parameterised modal formula which is guaranteed to characterise a `sensible' simulation equivalence.
		This template is used to construct an infinite family of equivalences which converges to weak bisimulation equivalence, and another infinite family which converges to congruence.
	www.cs.man.ac.uk /cstechrep/Abstracts/UMCS-96-1-1.html (131 words)

	Presheaf Models for Concurrency (Site not responding. Last check: 2007-10-31)
		In all but the case of the higher order calculus, open map bisimulation is proved to coincide with traditional notions of bisimulation for the process terms.
		For a fragment of the language, corresponding to a form of lambda-calculus, open map bisimulation coincides with applicative bisimulation.
		In developing a suitable general theory of domains, we extend results and notions, such as the limit-colimit coincidence theorem of Smyth and Plotkin, from the order-enriched case to a ``fully'' 2-categorical situation.
	www.daimi.au.dk /~luca/thesis.html (389 words)

	[No title]
		To: pratt@cs.stanford.edu Subject: bisimulations for higher dimensional automata Below I define the notion of bisimulation equivalence (and some related notions) for cubical sets (with initial state, final state, and labeling).
		I found it convenient to use a concrete representation rather then any of the two abstract ones (note that all the morphism information in the category of cubical sets is encoded in the 4 commutativities between s and t; a morphism that in one of your earlier mails was encoded as 001TT1T0 corresponds to s(0,s(1,t(2,t(5,(s(7))))))).
		I'm curious if more abstract and elegant definitions of bisimulation will turn out to be possible when working in a more abstract and elegant notion of cubical set.
	theory.stanford.edu /~rvg/hda (427 words)

	[No title] (Site not responding. Last check: 2007-10-31)
		The maximal strong and weak bisimulations on any class of processes can be obtained as the limits of decreasing chains of binary relations, approximants.
		In the case of strong bisimulation and Basic Process Algebras this chain has length at most omega which enables semidecidability of strong bisimilarity.
		We show that it is not so for weak bisimulation where the chain can grow much longer, and discuss the implications this has for the problem of (semi)decidability of weak bisimilarity.
	www.fi.muni.cz /reports/authors/Stribrna.html.iso-8859-1 (310 words)

	biblio
		Branching bisimulation for context-free processes 12 th FSTTCS, New Delhi, 1992, LNCS 652, pp.
		with O. Burkart and B. Steffen, Bisimulation collapse and the process taxonomy 7 th CONCUR 96, Pisa, 1996, LNCS 1119, pp.
		Bisimulation of context-free grammars and of pushdown automata CSLI Lecture Notes, 1995, Vol.
	www.irisa.fr /galion/caucal/biblio.html (394 words)

	Journal of the ACM Bibliography (Site not responding. Last check: 2007-10-31)
		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 \tau of CCS this is not the case.
		We also establish that for sequential processes observation equivalence is not preserved under refinement of actions, whereas branching bisimulation is.
		Bisimulation equivalence is decidable for all context-free processes.
	theory.lcs.mit.edu /~jacm/References/glabbeekw1996:555.html (396 words)

	A Process Algebra Diary (Site not responding. Last check: 2007-10-31)
		For the case of parallel composition, Moller showed that strong bisimulation equivalence is not finitely based over CCS and PA without the left merge operator.
		But, is the use of auxiliary operators necessary to give a finite axiomatization of bisimulation equivalence over the language BPA enriched with the mode transfer operators studied by Baeten and Bergstra in the aforementioned paper?
		In particular, we focus on BPA enriched with the interrupt operator, and show that, in the presence of two distinct actions, bisimulation equivalence is not finitely based over BPA with the interrupt operator.
	www.cs.auc.dk /~luca/PA-DIARY/02-11-2004.html (411 words)

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