934 research outputs found
Learning to Prove Safety over Parameterised Concurrent Systems (Full Version)
We revisit the classic problem of proving safety over parameterised
concurrent systems, i.e., an infinite family of finite-state concurrent systems
that are represented by some finite (symbolic) means. An example of such an
infinite family is a dining philosopher protocol with any number n of processes
(n being the parameter that defines the infinite family). Regular model
checking is a well-known generic framework for modelling parameterised
concurrent systems, where an infinite set of configurations (resp. transitions)
is represented by a regular set (resp. regular transducer). Although verifying
safety properties in the regular model checking framework is undecidable in
general, many sophisticated semi-algorithms have been developed in the past
fifteen years that can successfully prove safety in many practical instances.
In this paper, we propose a simple solution to synthesise regular inductive
invariants that makes use of Angluin's classic L* algorithm (and its variants).
We provide a termination guarantee when the set of configurations reachable
from a given set of initial configurations is regular. We have tested L*
algorithm on standard (as well as new) examples in regular model checking
including the dining philosopher protocol, the dining cryptographer protocol,
and several mutual exclusion protocols (e.g. Bakery, Burns, Szymanski, and
German). Our experiments show that, despite the simplicity of our solution, it
can perform at least as well as existing semi-algorithms.Comment: Full version of FMCAD'17 pape
Learning Linear Temporal Properties
We present two novel algorithms for learning formulas in Linear Temporal
Logic (LTL) from examples. The first learning algorithm reduces the learning
task to a series of satisfiability problems in propositional Boolean logic and
produces a smallest LTL formula (in terms of the number of subformulas) that is
consistent with the given data. Our second learning algorithm, on the other
hand, combines the SAT-based learning algorithm with classical algorithms for
learning decision trees. The result is a learning algorithm that scales to
real-world scenarios with hundreds of examples, but can no longer guarantee to
produce minimal consistent LTL formulas. We compare both learning algorithms
and demonstrate their performance on a wide range of synthetic benchmarks.
Additionally, we illustrate their usefulness on the task of understanding
executions of a leader election protocol
A Case Study in Formal System Engineering with SysML
International audienceIn the development of complex critical systems, an important source of errors is the misinterpretation of system requirements allocated to the software, due to inadequate communication between system engineering teams and software teams. In response, organizations that develop such systems are searching for solutions allowing formal system engineering and system to software bridging, based on standard languages like SysML. As part of this effort, we have defined a formal profile for SysML (OMEGA SysML) and we have built a simulation and verification toolbox for this profile (IFx). This paper reports on the experience of modelling and validating an industry-grade system, the Solar Generation System (SGS) of the Automated Transfer Vehicle (ATV) built by Astrium, using IFx-OMEGA. The experience reveals what can currently be expected from such an approach and what are the weak points that should be addressed by future research and development
A Complete Axiom System for Propositional Interval Temporal Logic with Infinite Time
Interval Temporal Logic (ITL) is an established temporal formalism for
reasoning about time periods. For over 25 years, it has been applied in a
number of ways and several ITL variants, axiom systems and tools have been
investigated. We solve the longstanding open problem of finding a complete
axiom system for basic quantifier-free propositional ITL (PITL) with infinite
time for analysing nonterminating computational systems. Our completeness proof
uses a reduction to completeness for PITL with finite time and conventional
propositional linear-time temporal logic. Unlike completeness proofs of equally
expressive logics with nonelementary computational complexity, our semantic
approach does not use tableaux, subformula closures or explicit deductions
involving encodings of omega automata and nontrivial techniques for
complementing them. We believe that our result also provides evidence of the
naturalness of interval-based reasoning
Formal Analysis of Concurrent Programs
In this thesis, extensions of Kleene algebras are used to develop algebras for rely-guarantee style reasoning about concurrent programs. In addition to these algebras, detailed denotational models are implemented in the interactive theorem prover Isabelle/HOL. Formal soundness proofs link the algebras to their models. This follows a general algebraic approach for developing correct by construction verification tools within Isabelle. In this approach, algebras provide inference rules and abstract principles for reasoning about the control flow of programs, while the concrete models provide laws for reasoning about data flow. This yields a rapid, lightweight approach for the construction of verification and refinement tools. These tools are used to construct a popular example from the literature, via refinement, within the context of a general-purpose interactive theorem proving environment
Polynomial Identification of omega-Automata
We study identification in the limit using polynomial time and data for
models of omega-automata. On the negative side we show that non-deterministic
omega-automata (of types Buchi, coBuchi, Parity, Rabin, Street, or Muller)
cannot be polynomially learned in the limit. On the positive side we show that
the omega-language classes IB, IC, IP, IR, IS, and IM, which are defined by
deterministic Buchi, coBuchi, Parity, Rabin, Streett, and Muller acceptors that
are isomorphic to their right-congruence automata, are identifiable in the
limit using polynomial time and data.
We give polynomial time inclusion and equivalence algorithms for
deterministic Buchi, coBuchi, Parity, Rabin, Streett, and Muller acceptors,
which are used to show that the characteristic samples for IB, IC, IP, IR, IS,
and IM can be constructed in polynomial time.
We also provide polynomial time algorithms to test whether a given
deterministic automaton of type X (for X in {B, C, P, R, S, M})is in the class
IX (i.e. recognizes a language that has a deterministic automaton that is
isomorphic to its right congruence automaton).Comment: This is an extended version of a paper with the same name that
appeared in TACAS2
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