Irek Ulidowski

CONCUR 2012 – Concurrency Theory

ion A Theory of History Dependent Abstractions for Learning Interface Automata . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240 Fides Aarts, Faranak Heidarian, and Frits Vaandrager Linearizability with Ownership Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256 Alexey Gotsman and Hongseok Yang Mobility and Space in Process Algebras Nested Protocols in Session Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272 Romain Demangeon and Kohei Honda Intensional and Extensional Characterisation of Global Progress in the π-Calculus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287 Luca Fossati, Kohei Honda, and Nobuko Yoshida Table of

Equivalences on observable processes

The finest observable and implementable equivalence on concurrent processes is sought as part of a larger program to develop a theory of observable processes where semantics of processes are based on locally and finitely observable process behavior and all process constructs are allowed, provided their operational meaning is defined by realistically implementable transition rules. The structure of transition rules is examined, and several conditions that all realistically implementable rules should satisfy are proposed. It is shown that the ISOS contexts capture exactly the observable behavior of processes. This leads to the result that copy plus refusal equivalence is the finest implementable equivalence.<<ETX>>

A Reversible Process Calculus and the Modelling of the ERK Signalling Pathway

We introduce a reversible process calculus with a new feature of execution control that allows us to change the direction and pattern of computation. This feature allows us to model a variety of modes of reverse computation, ranging from strict backtracking to reversing which respects causal ordering of events, and even reversing which violates causal ordering. The SOS rules that define the operators of the new calculus employ communication keys to handle communication correctly and key identifiers to control execution.

Ordered SOS process languages for branching and Eager bisimulation

We present a general and uniform method for defining structural operational semantics (SOS) of process operators by traditional Plotkin-style transition rules equipped with orderings. This new feature allows one to control the order of application of rules when deriving transitions of process terms. Our method is powerful enough to deal with rules with negative premises and copying. We show that rules with orderings, called ordered SOS rules, have the same expressive power as GSOS rules. We identify several classes of process languages with operators defined by rules with and without orderings in the setting with silent actions and divergence. We prove that branching bisimulation and eager bisimulation relations are preserved by all operators in process languages in the relevant classes.

Finite Axiom Systems for Testing Preorder and De Simone Process Languages

We propose a procedure for generating finite axiomatisations of testing preorder of De Nicola and Hennessy for De Simone process language. We also prove that testing preorder is preserved by all De Simone process operators. The usefulness of our results is illustrated in specification and verification of a (small) multi-media system. The important features of the system are suspension, resumption and alternation of execution of its components. We argue that the ability to use specially tailored De Simone operators allows to write clear and intuitive specifications. Moreover, the automatically generated axioms for such operators make the verification straightforward.

Extending Process Languages with Time

In recent years a large number of process languages with time have been developed as more realistic formalisms for description and reasoning about concurrent systems. We propose a uniform framework, based on the ordered structural operational semantics (SOS) approach, for extending arbitrary process languages with discrete time. The generality of our framework allows the user to select the most suitable timed process language for a task in hand. This is possible because the user can choose any operators, whether they are standard or new application-specific operators, provided that they preserve a version of weak bisimulation and all processes in the considered language satisfy the time determinacy property. We also propose several constraints on ordered SOS rules for the operators such that some other properties, which reflect the nature of time passage, are satisfied.

Reversibility and Models for Concurrency

There is a growing interest in models of reversible computation driven by exciting application areas such as bio-systems and quantum computing. Reversible process algebras RCCS [Danos, V. and J. Krivine, Reversible communicating systems, in: P. Gardner and N. Yoshida, editors, Proceedings of the 15th International Conference on Concurrency Theory CONCUR 2004, LNCS 3170 (2004), pp. 292-307] and CCSK [Phillips, I.C.C. and I. Ulidowski, Reversing algebraic process calculi, in: Proceedings of 9th International Conference on Foundations of Software Science and Computation Structures, FOSSACS 2006, LNCS 3921 (2006), pp. 246-260. Extended version accepted by Journal of Logic and Algebraic Programming] were developed and general techniques for reversing other process operators were proposed. The paper shows that the notion of reversibility can bridge the gap between some interleaving models and non-interleaving models of concurrency, and makes them interchangeable. We prove that transition systems associated with reversible process algebras are equivalent as models to labelled prime event structures. Furthermore, we show that forward-reverse bisimulation corresponds to hereditary history-preserving bisimulation in the setting with no auto-concurrency and no auto-causation.

Reversing algebraic process calculi

Reversible computation has a growing number of promising application areas such as the modelling of biochemical systems, program debugging and testing, and even programming languages for quantum computing. We formulate a procedure for converting operators of standard algebraic process calculi such as CCS, ACP and CSP into reversible operators, while preserving their operational semantics.

A Logic with Reverse Modalities for History-preserving Bisimulations

We introduce event identifier logic (EIL) which extends Henn essy-Milner logic by the addition of (1) reverse as well as forward modalities, and (2) identifier s to keep track of events. We show that this logic corresponds to hereditary history-preserv ing (HH) bisimulation equivalence within a particular true-concurrency model, namely stable configu ration structures. We furthermore show how natural sublogics of EIL correspond to coarser equivalences. In particular we provide logical characterisations of weak history-preserving (WH) and history-preserving (H) bisimulation. Logics corresponding to HH and H bisimulation have been given previously, but not to WH bisimulation (when autoconcurrency is allowed), as far as we are aware. We also present characteristic formulas which characterise individual structures with respect to h istory-preserving equivalences. The paper presents a modal logic that can express simple properties of computation in the true concurrency setting of stable configuration structures. We aim, li ke Hennessy-Milner logic (HML) [19] in the interleaving setting, to characterise the main true concur rency equivalences and to develop characteristic formulas for them. We focus in this paper on history-preserving bisimulation equivalences. HML has a “diamond” modality haiφ which says that an event labelled a can be performed, taking us to a new state which satisfies φ . The logic also contains negation (¬), conjunction (∧) and a base formula which always holds (tt). HML is strong enough to distinguish any two processes which are not bisimilar. We are interested in making true concurrency distinctions between processes. These processes will be event structures, where the current state is represented by the set of events w hich have occurred so far. Such sets are called configurations. Events have labels (ranged over by a, b,...), and different events may have the same label. We shall refer to example event structures using a CCS-like notation, with a| b denoting an event labelled with a in parallel with another labelled with b, a.b denoting two events labelled a and b where the first causes the second, and a+ b denoting two events labelled a and b which conflict.

A hierarchy of reverse bisimulations on stable configuration structures

Van Glabbeek and Goltz (and later Fecher) have investigated the relationships between various equivalences on stable configuration structures, including interleaving bisimulation (IB), step bisimulation (SB), pomset bisimulation and hereditary history-preserving (H-H) bisimulation. Since H-H bisimulation may be characterised by the use of reverse as well as forward transitions, it is of interest to investigate these and other forms of bisimulations where both forward and reverse transitions are allowed. Bednarczyk asked whether SB with reverse steps is as strong as H-H bisimulation. We answer this question negatively. We give various characterisations of SB with reverse steps, showing that forward steps do not add power. We strengthen Bednarczyks result that, in the absence of auto-concurrency, reverse IB is as strong as H-H bisimulation, by showing that we need only exclude auto-concurrent events at the same depth in the configuration. We consider several other forms of observations of reversible behaviour and define a wide range of bisimulations by mixing the forward and reverse observations. We investigate the power of these bisimulations and represent the relationships between them as a hierarchy with IB at the bottom and H-H at the top.