42,005 research outputs found
Procedure-modular specification and verification of temporal safety properties
This paper describes ProMoVer, a tool for fully automated procedure-modular verification of Java programs equipped with method-local and global assertions that specify safety properties of sequences of method invocations. Modularity at the procedure-level is a natural instantiation of the modular verification paradigm, where correctness of global properties is relativized on the local properties of the methods rather than on their implementations. Here, it is based on the construction of maximal models for a program model that abstracts away from program data. This approach allows global properties to be verified in the presence of code evolution, multiple method implementations (as arising from software product lines), or even unknown method implementations (as in mobile code for open platforms). ProMoVer automates a typical verification scenario for a previously developed tool set for compositional verification of control flow safety properties, and provides appropriate pre- and post-processing. Both linear-time temporal logic and finite automata are supported as formalisms for expressing local and global safety properties, allowing the user to choose a suitable format for the property at hand. Modularity is exploited by a mechanism for proof reuse that detects and minimizes the verification tasks resulting from changes in the code and the specifications. The verification task is relatively light-weight due to support for abstraction from private methods and automatic extraction of candidate specifications from method implementations. We evaluate the tool on a number of applications from the domains of Java Card and web-based application
Reasoning about history based access control policy using past time operators of interval temporal logic
Interval Temporal Logic (ITL) is a flexible notation for the propositional and first-order logical reasoning about periods of time that exist in specifications of hardware and software systems.
ITL is different from other temporal logics since it can deal with both sequential and parallel composition and provides powerful and extensible specification and verification methods for reasoning about properties such as safety, time projection and liveness.
Most imperative programming constructs can be seen as ITL formula that form the basis of an executable framework called Tempura that is used for the development and testing of ITL specifications.\\
ITL has only future operators, but the use of past operators make specifications referring to history more succinct; that is, there are classes of properties that can be expressed by means of much shorter formulas.
What is more, statements are easier to express (simplicity) when past operators are included. Moreover, using past operators does not increase the complexity of interval temporal logic regarding the formula size and the simplicity.
This thesis introduces past time of interval temporal logic where, instead of future time operators Chop, Chopstar, and Skip, we have past operators past Chop, past Chopstar and past Skip.
The syntax and semantics of past time ITL are given together with its axiom and proof system. Furthermore, Security Analysis Toolkit for Agents (SANTA) operators such always-followed-by and the strong version of it has been given history based semantics using past time operators.
In order to evaluate past time interval temporal logic, the problem of specification, verification of history based access control policies has been selected. This problem has already been solved using future time of interval temporal logic ITL but the drawback is that policy rules are not succinct and simple. However, the use of past time operators of ITL produces simple and succinct policy rules.
The verification technique used to proof the safety property of history based access control policies is adapted for past time ITL to show that past time operators of interval temporal logic can specify and verify a security
scenario such as history based access control policy
From Uncertainty Data to Robust Policies for Temporal Logic Planning
We consider the problem of synthesizing robust disturbance feedback policies
for systems performing complex tasks. We formulate the tasks as linear temporal
logic specifications and encode them into an optimization framework via
mixed-integer constraints. Both the system dynamics and the specifications are
known but affected by uncertainty. The distribution of the uncertainty is
unknown, however realizations can be obtained. We introduce a data-driven
approach where the constraints are fulfilled for a set of realizations and
provide probabilistic generalization guarantees as a function of the number of
considered realizations. We use separate chance constraints for the
satisfaction of the specification and operational constraints. This allows us
to quantify their violation probabilities independently. We compute disturbance
feedback policies as solutions of mixed-integer linear or quadratic
optimization problems. By using feedback we can exploit information of past
realizations and provide feasibility for a wider range of situations compared
to static input sequences. We demonstrate the proposed method on two robust
motion-planning case studies for autonomous driving
Prescribed Performance Control Guided Policy Improvement for Satisfying Signal Temporal Logic Tasks
Signal temporal logic (STL) provides a user-friendly interface for defining
complex tasks for robotic systems. Recent efforts aim at designing control laws
or using reinforcement learning methods to find policies which guarantee
satisfaction of these tasks. While the former suffer from the trade-off between
task specification and computational complexity, the latter encounter
difficulties in exploration as the tasks become more complex and challenging to
satisfy. This paper proposes to combine the benefits of the two approaches and
use an efficient prescribed performance control (PPC) base law to guide
exploration within the reinforcement learning algorithm. The potential of the
method is demonstrated in a simulated environment through two sample
navigational tasks.Comment: This is the extended version of the paper accepted to the 2019
American Control Conference (ACC), Philadelphia (to be published
Formalization and Validation of Safety-Critical Requirements
The validation of requirements is a fundamental step in the development
process of safety-critical systems. In safety critical applications such as
aerospace, avionics and railways, the use of formal methods is of paramount
importance both for requirements and for design validation. Nevertheless, while
for the verification of the design, many formal techniques have been conceived
and applied, the research on formal methods for requirements validation is not
yet mature. The main obstacles are that, on the one hand, the correctness of
requirements is not formally defined; on the other hand that the formalization
and the validation of the requirements usually demands a strong involvement of
domain experts. We report on a methodology and a series of techniques that we
developed for the formalization and validation of high-level requirements for
safety-critical applications. The main ingredients are a very expressive formal
language and automatic satisfiability procedures. The language combines
first-order, temporal, and hybrid logic. The satisfiability procedures are
based on model checking and satisfiability modulo theory. We applied this
technology within an industrial project to the validation of railways
requirements
Decentralized Motion Planning with Collision Avoidance for a Team of UAVs under High Level Goals
This paper addresses the motion planning problem for a team of aerial agents
under high level goals. We propose a hybrid control strategy that guarantees
the accomplishment of each agent's local goal specification, which is given as
a temporal logic formula, while guaranteeing inter-agent collision avoidance.
In particular, by defining 3-D spheres that bound the agents' volume, we extend
previous work on decentralized navigation functions and propose control laws
that navigate the agents among predefined regions of interest of the workspace
while avoiding collision with each other. This allows us to abstract the motion
of the agents as finite transition systems and, by employing standard formal
verification techniques, to derive a high-level control algorithm that
satisfies the agents' specifications. Simulation and experimental results with
quadrotors verify the validity of the proposed method.Comment: Submitted to the IEEE International Conference on Robotics and
Automation (ICRA), Singapore, 201
Model-Based Testing of Safety Critical Real-Time Control Logic Software
The paper presents the experience of the authors in model based testing of
safety critical real-time control logic software. It describes specifics of the
corresponding industrial settings and discusses technical details of usage of
UniTESK model based testing technology in these settings. Finally, we discuss
possible future directions of safety critical software development processes
and a place of model based testing techniques in it.Comment: In Proceedings MBT 2012, arXiv:1202.582
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