36,789 research outputs found
Robust Linear Temporal Logic
Although it is widely accepted that every system should be robust, in the
sense that "small" violations of environment assumptions should lead to "small"
violations of system guarantees, it is less clear how to make this intuitive
notion of robustness mathematically precise. In this paper, we address this
problem by developing a robust version of Linear Temporal Logic (LTL), which we
call robust LTL and denote by rLTL. Formulas in rLTL are syntactically
identical to LTL formulas but are endowed with a many-valued semantics that
encodes robustness. In particular, the semantics of the rLTL formula is such that a "small" violation of the environment
assumption is guaranteed to only produce a "small" violation of the
system guarantee . In addition to introducing rLTL, we study the
verification and synthesis problems for this logic: similarly to LTL, we show
that both problems are decidable, that the verification problem can be solved
in time exponential in the number of subformulas of the rLTL formula at hand,
and that the synthesis problem can be solved in doubly exponential time
Sciduction: Combining Induction, Deduction, and Structure for Verification and Synthesis
Even with impressive advances in automated formal methods, certain problems
in system verification and synthesis remain challenging. Examples include the
verification of quantitative properties of software involving constraints on
timing and energy consumption, and the automatic synthesis of systems from
specifications. The major challenges include environment modeling,
incompleteness in specifications, and the complexity of underlying decision
problems.
This position paper proposes sciduction, an approach to tackle these
challenges by integrating inductive inference, deductive reasoning, and
structure hypotheses. Deductive reasoning, which leads from general rules or
concepts to conclusions about specific problem instances, includes techniques
such as logical inference and constraint solving. Inductive inference, which
generalizes from specific instances to yield a concept, includes algorithmic
learning from examples. Structure hypotheses are used to define the class of
artifacts, such as invariants or program fragments, generated during
verification or synthesis. Sciduction constrains inductive and deductive
reasoning using structure hypotheses, and actively combines inductive and
deductive reasoning: for instance, deductive techniques generate examples for
learning, and inductive reasoning is used to guide the deductive engines.
We illustrate this approach with three applications: (i) timing analysis of
software; (ii) synthesis of loop-free programs, and (iii) controller synthesis
for hybrid systems. Some future applications are also discussed
Model checking embedded system designs
We survey the basic principles behind the application of model checking to controller verification and synthesis. A promising development is the area of guided model checking, in which the state space search strategy of the model checking algorithm can be influenced to visit more interesting sets of states first. In particular, we discuss how model checking can be combined with heuristic cost functions to guide search strategies. Finally, we list a number of current research developments, especially in the area of reachability analysis for optimal control and related issues
Exploiting the Temporal Logic Hierarchy and the Non-Confluence Property for Efficient LTL Synthesis
The classic approaches to synthesize a reactive system from a linear temporal
logic (LTL) specification first translate the given LTL formula to an
equivalent omega-automaton and then compute a winning strategy for the
corresponding omega-regular game. To this end, the obtained omega-automata have
to be (pseudo)-determinized where typically a variant of Safra's
determinization procedure is used. In this paper, we show that this
determinization step can be significantly improved for tool implementations by
replacing Safra's determinization by simpler determinization procedures. In
particular, we exploit (1) the temporal logic hierarchy that corresponds to the
well-known automata hierarchy consisting of safety, liveness, Buechi, and
co-Buechi automata as well as their boolean closures, (2) the non-confluence
property of omega-automata that result from certain translations of LTL
formulas, and (3) symbolic implementations of determinization procedures for
the Rabin-Scott and the Miyano-Hayashi breakpoint construction. In particular,
we present convincing experimental results that demonstrate the practical
applicability of our new synthesis procedure
Rapid Recovery for Systems with Scarce Faults
Our goal is to achieve a high degree of fault tolerance through the control
of a safety critical systems. This reduces to solving a game between a
malicious environment that injects failures and a controller who tries to
establish a correct behavior. We suggest a new control objective for such
systems that offers a better balance between complexity and precision: we seek
systems that are k-resilient. In order to be k-resilient, a system needs to be
able to rapidly recover from a small number, up to k, of local faults
infinitely many times, provided that blocks of up to k faults are separated by
short recovery periods in which no fault occurs. k-resilience is a simple but
powerful abstraction from the precise distribution of local faults, but much
more refined than the traditional objective to maximize the number of local
faults. We argue why we believe this to be the right level of abstraction for
safety critical systems when local faults are few and far between. We show that
the computational complexity of constructing optimal control with respect to
resilience is low and demonstrate the feasibility through an implementation and
experimental results.Comment: In Proceedings GandALF 2012, arXiv:1210.202
Benchmarks for Parity Games (extended version)
We propose a benchmark suite for parity games that includes all benchmarks
that have been used in the literature, and make it available online. We give an
overview of the parity games, including a description of how they have been
generated. We also describe structural properties of parity games, and using
these properties we show that our benchmarks are representative. With this work
we provide a starting point for further experimentation with parity games.Comment: The corresponding tool and benchmarks are available from
https://github.com/jkeiren/paritygame-generator. This is an extended version
of the paper that has been accepted for FSEN 201
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