2,944 research outputs found
Parameterized Synthesis
We study the synthesis problem for distributed architectures with a
parametric number of finite-state components. Parameterized specifications
arise naturally in a synthesis setting, but thus far it was unclear how to
detect realizability and how to perform synthesis in a parameterized setting.
Using a classical result from verification, we show that for a class of
specifications in indexed LTL\X, parameterized synthesis in token ring networks
is equivalent to distributed synthesis in a network consisting of a few copies
of a single process. Adapting a well-known result from distributed synthesis,
we show that the latter problem is undecidable. We describe a semi-decision
procedure for the parameterized synthesis problem in token rings, based on
bounded synthesis. We extend the approach to parameterized synthesis in
token-passing networks with arbitrary topologies, and show applicability on a
simple case study. Finally, we sketch a general framework for parameterized
synthesis based on cutoffs and other parameterized verification techniques.Comment: Extended version of TACAS 2012 paper, 29 page
Parameterized Model-Checking for Timed-Systems with Conjunctive Guards (Extended Version)
In this work we extend the Emerson and Kahlon's cutoff theorems for process
skeletons with conjunctive guards to Parameterized Networks of Timed Automata,
i.e. systems obtained by an \emph{apriori} unknown number of Timed Automata
instantiated from a finite set of Timed Automata templates.
In this way we aim at giving a tool to universally verify software systems
where an unknown number of software components (i.e. processes) interact with
continuous time temporal constraints. It is often the case, indeed, that
distributed algorithms show an heterogeneous nature, combining dynamic aspects
with real-time aspects. In the paper we will also show how to model check a
protocol that uses special variables storing identifiers of the participating
processes (i.e. PIDs) in Timed Automata with conjunctive guards. This is
non-trivial, since solutions to the parameterized verification problem often
relies on the processes to be symmetric, i.e. indistinguishable. On the other
side, many popular distributed algorithms make use of PIDs and thus cannot
directly apply those solutions
Using Flow Specifications of Parameterized Cache Coherence Protocols for Verifying Deadlock Freedom
We consider the problem of verifying deadlock freedom for symmetric cache
coherence protocols. In particular, we focus on a specific form of deadlock
which is useful for the cache coherence protocol domain and consistent with the
internal definition of deadlock in the Murphi model checker: we refer to this
deadlock as a system- wide deadlock (s-deadlock). In s-deadlock, the entire
system gets blocked and is unable to make any transition. Cache coherence
protocols consist of N symmetric cache agents, where N is an unbounded
parameter; thus the verification of s-deadlock freedom is naturally a
parameterized verification problem. Parametrized verification techniques work
by using sound abstractions to reduce the unbounded model to a bounded model.
Efficient abstractions which work well for industrial scale protocols typically
bound the model by replacing the state of most of the agents by an abstract
environment, while keeping just one or two agents as is. However, leveraging
such efficient abstractions becomes a challenge for s-deadlock: a violation of
s-deadlock is a state in which the transitions of all of the unbounded number
of agents cannot occur and so a simple abstraction like the one above will not
preserve this violation. In this work we address this challenge by presenting a
technique which leverages high-level information about the protocols, in the
form of message sequence dia- grams referred to as flows, for constructing
invariants that are collectively stronger than s-deadlock. Efficient
abstractions can be constructed to verify these invariants. We successfully
verify the German and Flash protocols using our technique
Efficient First-Order Temporal Logic for Infinite-State Systems
In this paper we consider the specification and verification of
infinite-state systems using temporal logic. In particular, we describe
parameterised systems using a new variety of first-order temporal logic that is
both powerful enough for this form of specification and tractable enough for
practical deductive verification. Importantly, the power of the temporal
language allows us to describe (and verify) asynchronous systems, communication
delays and more complex properties such as liveness and fairness properties.
These aspects appear difficult for many other approaches to infinite-state
verification.Comment: 16 pages, 2 figure
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