947 research outputs found
On Modelling and Analysis of Dynamic Reconfiguration of Dependable Real-Time Systems
This paper motivates the need for a formalism for the modelling and analysis
of dynamic reconfiguration of dependable real-time systems. We present
requirements that the formalism must meet, and use these to evaluate well
established formalisms and two process algebras that we have been developing,
namely, Webpi and CCSdp. A simple case study is developed to illustrate the
modelling power of these two formalisms. The paper shows how Webpi and CCSdp
represent a significant step forward in modelling adaptive and dependable
real-time systems.Comment: Presented and published at DEPEND 201
Verification and Synthesis of Symmetric Uni-Rings for Leads-To Properties
This paper investigates the verification and synthesis of parameterized
protocols that satisfy leadsto properties on symmetric
unidirectional rings (a.k.a. uni-rings) of deterministic and constant-space
processes under no fairness and interleaving semantics, where and are
global state predicates. First, we show that verifying for
parameterized protocols on symmetric uni-rings is undecidable, even for
deterministic and constant-space processes, and conjunctive state predicates.
Then, we show that surprisingly synthesizing symmetric uni-ring protocols that
satisfy is actually decidable. We identify necessary and
sufficient conditions for the decidability of synthesis based on which we
devise a sound and complete polynomial-time algorithm that takes the predicates
and , and automatically generates a parameterized protocol that
satisfies for unbounded (but finite) ring sizes. Moreover, we
present some decidability results for cases where leadsto is required from
multiple distinct predicates to different predicates. To demonstrate
the practicality of our synthesis method, we synthesize some parameterized
protocols, including agreement and parity protocols
Process Algebra, CCS, and Bisimulation Decidability
Over the past fifteen years, there has been intensive study of formal systems that can model concurrency and communication. Two such systems are the Calculus of Communicating Systems, and the Algebra of Communicating Processes. The objective of this paper has two aspects; (1) to study the characteristics and features of these two systems, and (2) to investigate two interesting formal proofs concerning issues of decidability of bisimulation equivalence in these systems. An examination of the processes that generate context-free languages as a trace set shows that their bisimulation equivalence is decidable, in contrast to the undecidability of their trace set equivalence. Recent results have also shown that the bisimulation equivalence problem for processes with a limited amount of concurrency is decidable
Subclasses of Formalized Data Flow Diagrams: Monogeneous, Linear & Topologically Free Choice RDFD\u27s
Formalized Data Flow Diagrams (FDFD\u27s) and, especially, Reduced Data Flow Diagrams (RDFD\u27s) are Turing equivalent (Symanzik and Baker, 1996). Therefore, no decidability problem can be solved for FDFD\u27s in general. However, it is possible to define subclasses of FDFD\u27s for which decidability problems can be answered. In this paper we will define certain subclasses of FDFD\u27s, which we call Monogeneous RDFD\u27s, Linear RDFD\u27s, and Topologically Free Choice RDFD\u27s. We will show that two of these three subclasses of FDFD\u27s can be simulated via isomorphism by the correspondingly named subclasses of FIFO Petri Nets. It is known that isomorphisms between computation systems guarantee the same answers to corresponding decidability problems (e. g., reachability, deadlock, liveness) in the two systems (Kasai and Miller, 1982). This means that problems where it is known that they can (not) be solved for a subclass of FIFO Petri Nets it follows immediately that the same problems can (not) be solved for the correspondingly named subclass of FDFD\u27s
Connectors meet Choreographies
We present Cho-Reo-graphies (CR), a new language model that unites two
powerful programming paradigms for concurrent software based on communicating
processes: Choreographic Programming and Exogenous Coordination. In CR,
programmers specify the desired communications among processes using a
choreography, and define how communications should be concretely animated by
connectors given as constraint automata (e.g., synchronous barriers and
asynchronous multi-casts). CR is the first choreography calculus where
different communication semantics (determined by connectors) can be freely
mixed; since connectors are user-defined, CR also supports many communication
semantics that were previously unavailable for choreographies. We develop a
static analysis that guarantees that a choreography in CR and its user-defined
connectors are compatible, define a compiler from choreographies to a process
calculus based on connectors, and prove that compatibility guarantees
deadlock-freedom of the compiled process implementations
A Polynomial Translation of pi-calculus FCPs to Safe Petri Nets
We develop a polynomial translation from finite control pi-calculus processes
to safe low-level Petri nets. To our knowledge, this is the first such
translation. It is natural in that there is a close correspondence between the
control flows, enjoys a bisimulation result, and is suitable for practical
model checking.Comment: To appear in special issue on best papers of CONCUR'12 of Logical
Methods in Computer Scienc
Decidability Issues for Petri Nets
This is a survey of some decidability results for Petri nets, covering the last three decades. The presentation is structured around decidability of specific properties, various behavioural equivalences and finally the model checking problem for temporal logics
Petri Games: Synthesis of Distributed Systems with Causal Memory
We present a new multiplayer game model for the interaction and the flow of
information in a distributed system. The players are tokens on a Petri net. As
long as the players move in independent parts of the net, they do not know of
each other; when they synchronize at a joint transition, each player gets
informed of the causal history of the other player. We show that for Petri
games with a single environment player and an arbitrary bounded number of
system players, deciding the existence of a safety strategy for the system
players is EXPTIME-complete.Comment: In Proceedings GandALF 2014, arXiv:1408.556
Translating Asynchronous Games for Distributed Synthesis (Full Version)
In distributed synthesis, we generate a set of process implementations that,
together, accomplish an objective against all possible behaviors of the
environment. A lot of recent work has focussed on systems with causal memory,
i.e., sets of asynchronous processes that exchange their causal histories upon
synchronization. Decidability results for this problem have been stated either
in terms of control games, which extend Zielonka's asynchronous automata by
partitioning the actions into controllable and uncontrollable, or in terms of
Petri games, which extend Petri nets by partitioning the tokens into system and
environment players. The precise connection between these two models was so
far, however, an open question. In this paper, we provide the first formal
connection between control games and Petri games. We establish the equivalence
of the two game models based on weak bisimulations between their strategies.
For both directions, we show that a game of one type can be translated into an
equivalent game of the other type. We provide exponential upper and lower
bounds for the translations. Our translations make it possible to transfer and
combine decidability results between the two types of games. Exemplarily, we
translate decidability in acyclic communication architectures, originally
obtained for control games, to Petri games, and decidability in single-process
systems, originally obtained for Petri games, to control games
Adaptable processes
We propose the concept of adaptable processes as a way of overcoming the
limitations that process calculi have for describing patterns of dynamic
process evolution. Such patterns rely on direct ways of controlling the
behavior and location of running processes, and so they are at the heart of the
adaptation capabilities present in many modern concurrent systems. Adaptable
processes have a location and are sensible to actions of dynamic update at
runtime; this allows to express a wide range of evolvability patterns for
concurrent processes. We introduce a core calculus of adaptable processes and
propose two verification problems for them: bounded and eventual adaptation.
While the former ensures that the number of consecutive erroneous states that
can be traversed during a computation is bound by some given number k, the
latter ensures that if the system enters into a state with errors then a state
without errors will be eventually reached. We study the (un)decidability of
these two problems in several variants of the calculus, which result from
considering dynamic and static topologies of adaptable processes as well as
different evolvability patterns. Rather than a specification language, our
calculus intends to be a basis for investigating the fundamental properties of
evolvable processes and for developing richer languages with evolvability
capabilities
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