Similarity testing for access control

ContextAccess control is among the most important security mechanisms, and XACML is the de facto standard for specifying, storing and deploying access control policies. Since it is critical that enforced policies are correct, policy testing must be performed in an effective way to identify potential security flaws and bugs. In practice, exhaustive testing is impossible due to budget constraints. Therefore the tests need to be prioritized so that resources are focused on their most relevant subset.ObjectiveThis paper tackles the issue of access control test prioritization. It proposes a new approach for access control test prioritization that relies on similarity.MethodThe approach has been applied to several policies and the results have been compared to random prioritization (as a baseline). To assess the different prioritization criteria, we use mutation analysis and compute the mutation scores reached by each criterion. This helps assessing the rate of fault detection.ResultsThe empirical results indicate that our proposed approach is effective and its rate of fault detection is higher than that of random prioritization.ConclusionWe conclude that prioritization of access control test cases can be usefully based on similarity criteria.     

Files d'attente exponentielles ayant des parametres non-stationnaires dans le temps

Summary There exist a large number of Queueing Systems having a non-stationary behavior. We call non-stationarity, random time-variations of some parameters of the system (i.e. the input or service rates). A typical example is a reliability system which corresponds to the unpredictable breakdown or failure of the server. Random intensity models are natural for describing such phenomena.We introduce a model with randomly changing service rate. It does not obey a certain independence assumption often made in Queueing Theory. A complete analysis of the model is carried out, explicit results and performance curves are given. Jury's criteria are used to find Necessary and Sufficient Conditions for Stability. These criteria are easy to use and allow us to find the conditions of stability which were not obtained in many previous studies.     

Certainty equivalence adaptation combined with super-twisting sliding-mode control

ABSTRACT

In this paper, a Lyapunov-based control concept is presented that combines variable structure and adaptive control. The considered system class consists of nonlinear single input systems which are affected by matched structured and unstructured uncertainties. Resorting to the certainty equivalence principle, the controller exploits advantages of both the sliding-mode and the adaptive control methodology. It is demonstrated that the gains of the discontinuous control action may be reduced remarkably when compared with pure sliding-mode-based approaches. The efficiency of the presented concept is demonstrated in detail, using results of numerical simulations.     

Suitability assessment framework of agent-based software architectures

ContextA common distributed intelligent system architecture is Multi Agent Systems (MASs). Creating systems with this architecture has been recently supported by Agent Oriented Software Engineering (AOSE) methodologies. But two questions remain: how do we determine the suitability of a MAS implementation for a particular problem? And can this be determined without AOSE expertise?ObjectiveGiven the relatively small number of software engineers that are AOSE experts, many problems that could be better solved with a MAS system are solved using more commonly known but not necessarily as suitable development approaches (e.g. object-oriented). The paper aims to empower software engineers, who are not necessarily AOSE experts, in deciding whether or not they should advocate the use of an MAS technology for a given project.MethodThe paper will construct a systematic framework to identify key criteria in a problem requirement definition to assess the suitability of a MAS solution. The criteria are first identified using an iterative process. The features are initially identified from MAS implementations, and then validated against related work. This is followed by a statistical analysis of 25 problems that characterise agent-oriented solutions previously developed to group features into key criteria.ResultsKey criteria were sufficiently prominent using factor analysis to construct a framework which provides a process that identifies within the requirements the criteria discovered. This framework is then evaluated for assessing suitability of a MAS architecture, by non-AOSE experts, on two real world problems: an electricity market simulation and a financial accounting system.ConclusionSubstituting a software engineer’s personal inclination to (or not to) use a MAS, our framework provides an objective mechanism. It can supplant current practices where the decision to use a MAS architecture for a given problem remains an informal process. It was successfully illustrated on two real world problems to assess the suitability of a MAS implementation. This paper will potentially facilitate the take up of MAS technology.     

Further results on the robust stability for neutral-type Lur’e system with mixed delays and sector-bounded nonlinearities

This paper is concerned with the robust stability for neutral-type Lur’e system with mixed time-varying delays. By combining the delay-fraction theory with the reciprocally convex method andWirtinger-based inequality technology, some new delay-derivative-dependent stability criteria are derived via a modified Lyapunov-Krasovskii functional (LKF) approach. The criteria are less conservative than some previous ones.

     

Stochastic maximum principle for delayed doubly stochastic control systems and their applications

ABSTRACT

In this paper, we investigate the optimal control problems for delayed doubly stochastic control systems. We first discuss the existence and uniqueness of the delayed doubly stochastic differential equation by martingale representation theorem and contraction mapping principle. As a necessary condition of the optimal control, we deduce a stochastic maximum principle under some assumption. At the same time, a sufficient condition of optimality is obtained by using the duality method. At the end of the paper, we apply our stochastic maximum principle to a class of linear quadratic optimal control problem and obtain the explicit expression of the optimal control.     

On optimal control of mean-field stochastic systems driven by Teugels martingales via derivative with respect to measures

ABSTRACT

This paper deals with partial information stochastic optimal control problem for general controlled mean-field systems driven by Teugels martingales associated with some Lévy process having moments of all orders, and an independent Brownian motion. The coefficients of the system depend on the state of the solution process as well as of its probability law and the control variable. We establish a set of necessary conditions in the form of Pontryagin maximum principle for the optimal control. We also give additional conditions, under which the necessary optimality conditions turn out to be sufficient. The proof of our result is based on the derivative with respect to the probability law by applying Lions derivatives and a corresponding Itô formula. As an application, conditional mean-variance portfolio selection problem in incomplete market, where the system is governed by some Gamma process is studied to illustrate our theoretical results.     

The effect of scale-side,indicator type,and control plane on direction-of-turn stereotypes for Hong Kong Chinese subjects

Abstract

This study investigates the influence of scale-side, pointer type, direction-of-increase, and control plane on direction-of-turn stereotypes for Chinese subjects using a variety of configurations of a linear display with a rotary control. Pointer type and direction of increase did not have a significant effect on direction-of-turn expectation. Strong stereotypes are found when Warrick's principle and the scale-side principle do not clash. In such a configuration, the scale is on the opposite side of the display to the control, and the display indicator moves in the same plane as the control. However, when the two principles clash, stereotypes are weakened or eliminated and no single principle dominates. For a rotary control placed to the right of a horizontal linear scale in the frontal plane there are strong clockwise-for-right and counterclockwise-for-left stereotypes which dominate the scale-side principle when there is a clash. The most marked stereotypes and fastest response times are obtained for the horizontal display with the control in the same frontal plane     

Generating semantically valid test inputs using constrained input grammars

ContextGenerating test cases based on software input interface is a black-box testing technique that can be made more effective by using structured input models such as input grammars. Automatically generating grammar-based test inputs may lead to structurally valid but semantically invalid inputs that may be rejected in early semantic error checking phases of a system under test.ObjectiveThis paper aims to introduce a method for specifying a grammar-based input model with the model’s semantic constraints to be used in the generation of positive test inputs. It is also important that the method can generate effective test suites based on appropriate grammar-based coverage criteria.MethodFormal specification of both input structure and input semantics provides the opportunity to use model instantiation techniques to create model instances that satisfy all specified constraints. The input interface of a subject system can be specified using a high-level specification scheme such as attribute grammars, and a transformation function from this scheme to an instantiable formal modeling language can generate the desired model instances.ResultsWe propose a declarative grammar-based input specification method that is based on a variation of attribute grammars and allows the user to specify input constraints in addition to input structure. The model can be instantiated automatically to generate structurally and semantically valid test inputs. The proposed method has the capability to specify test requirements and coverage criteria and use them to generate valid test suites that satisfy test coverage criteria requirements.ConclusionThe work presented in this paper provides a black-box test generation method for grammar-based software inputs that can automatically generate criteria-covering test suites.     

TECHNICAL NOTE: Design criteria for microclimate cooling systems

Abstract

This paper identifies and described 25 design criteria that are desirable characteristics for a microclimate cooling system (MCCS). These criteria can be used as a check list by designers when developing an MCCS, and by organizations when evaluating and selecting MCCSs for use by their employees.     

Input-to-state stability of stochastic nonlinear fuzzy Cohen–Grossberg neural networks with the event-triggered control

ABSTRACT

In this paper, we investigate a class of stochastic nonlinear fuzzy Cohen–Grossberg neural networks with feedback control and an unknown exogenous disturbance. By using the Lyapunov function, Itô's formula, Dynkin's formula, Comparison principle and stochastic analysis theory, we show that the considered system is input-to-state stable with the help of the designed event-triggered mechanism. Moreover, we also guarantee that the internal execution time intervals of control task will not be arbitrarily small. Finally, some remarks and discussions have been provided to show that our results are meaningful.     

Global stabilisation via time-varying output feedback for the systems with inherent nonlinearities and coarse disturbance

ABSTRACT

This paper is devoted to the global output-feedback stabilisation for a class of nonlinear systems with inherent nonlinearities and coarse disturbance. Remarkably, the disturbance may be non-periodic, non-differentiable and/or of unknown magnitude, and hence some critical requirements on the disturbance in the existing related literature are successfully removed. Recognising that the strategies of disturbance compensation, such as internal model principle, sliding mode control method, learning method and active disturbance rejection control method, are quite hard or even impossible to apply, a time-varying design scheme is developed in the paper. Moreover, the serious unknowns and time-variations reflected in the growth rate of the system are also dealt with by the proposed scheme. By designing a time-varying output-feedback controller, all the signals of the resulting closed-loop system are globally bounded, and the original system state and the observer state ultimately converge to zero.     

Interpolating sliding mode observer for a ball and beam system

ABSTRACT

A principle of interpolating sliding mode observer is introduced in this paper. The observer incorporates multiple linear observers through interpolation of multiple estimates, which is treated as a type of adaptation. The principle is then applied to the ball and beam system for observation of the slope of the beam from the measurement of the ball position. The linearised model of the ball and beam system using multiple linearisation points is developed. The observer dynamics implemented in Matlab/Simulink Real Time Workshop environment. Experiments conducted on the ball and beam experimental setup demonstrate excellent performance of the designed novel interpolating (adaptive) observer.     

Decentralised adaptive neural connectively finite-time control for a class of p-normal form large-scale nonlinear systems

ABSTRACT

This paper focuses on the decentralised adaptive finite-time connective stabilisation problem for a class of p-normal form large-scale nonlinear systems at the first. By combining the adding a power integrator technique, the neural network technique and the finite-time Lyapunov stability theory, the decentralised adaptive neural finite-time controllers are designed, which can guarantee the large-scale system is finite-time connectively stable. In order to avoid the effect of neural network estimation error on satisfying the finite-time criteria, the combination vectors are composed by the weights and the estimation errors of the neural networks. The maximal upper bounds of the combination vector norms are taken as the adaptive parameters. Because of employing neural networks, the restriction of the unknown nonlinear terms in some literature about finite-time control is relaxed. Two simulation examples are provided to prove the effectiveness and advantage of the proposed control method.     

The development of driver assistance systems following usability criteria

Increasing numbers of intelligent driver assistance systems are now being installed in motor vehicles to support drivers. In order to ensure that the stress reduction benefits obtained from these systems are not nullified or even outweighed by new stresses at the vehicle's man-machine interfaces, the systems' control concepts must be designed to high ergonomic standards. This paper seeks to identify design weaknesses in assistance systems by presenting criteria that must, on the one hand, be observed when designing the control concept of a new assistance system and, on the other hand, be applied when assessing the man-machine interfaces of assistance systems already installed in a vehicle.     

Optimization of shift work: physiological contributions

Abstract

Healthy subjects (n= 62) with different circadian phase positions worked up to six weeks in different shift systems. Rotation speed was experimentally varied. On shift days all subjects worked in the Institute but spent their leisure time as usual.

In order to minimize bias through masking effects, ‘control days’ were interpolated (twice a week) into the shift periods. On these control days subjects remained on bedrest for 24 hours under constant conditions.

Results were as follows:

(i) The earlier the circadian phase position the poorer the adaptation to night-shifts. In particular, morning types were not able to adapt even to permanent night-shifts.

(ii) Evening types were able to adjust their circadian systems to a slowly rotating shift system (rotation speed seven days) and a 25 h-sliding system though they failed to do so with more quickly rotating systems. Whereas indifferent subjects were not able to adjust to even the slowly rotating system.

(iii) When stable phase shifts occurred in response to altered working hours they always amounted to about one hour per day if the working hours were not coherent with the usual environmental zeitgebers.

It is concluded that, on physiological criteria, very slow rotating shift systems or permanent night-shifts seem to be acceptable for evening types, but not for morning types who may require special health care in these conditions.     

Task orientation and user‐oriented dialog design

Work psychologists have introduced a concept, in which dialog design is a part of task design. A set of criteria of user‐oriented dialog design is presented here. These criteria are consistently integrated into a control concept. Empirical investigations on some of these criteria are then described. In an experiment to prove the criterion transparency, a desktop interface (high transparency) and a conventional menu selection interface (low transparency) were compared. The main result is the clear superiority of the user interface with direct manipulation over the conventional user interface with menu selection. Support is another of the criteria of user‐oriented dialog design that was empirically investigated. The advantages of goal‐ and task‐oriented help messages are also described here. To make the criterion flexibility and the criterion user‐definability practicable, the implementation of a dialog handler for user‐tailorable systems is introduced. The criterion participation was investigated in field studies. It will be shown that in projects with active participation the costs were exceeded to a lesser degree than in projects with passive participation and to a much lesser degree than in projects without participation.     

An approach and tool for measurement of state variable based data-flow test coverage for aspect-oriented programs

ContextData-flow testing approaches have been used for procedural and object-oriented programs, and shown to be effective in detecting faults. However, few such approaches have been evaluated for aspect-oriented programs. In such programs, data-flow interactions can occur between base classes and aspects, which can affect the behavior of both. Faults resulting from such interactions are hard to detect unless the interactions are specifically targeted during testing.ObjectiveThis paper presents an approach and tool implementation for measuring data-flow coverage based on state variables defined in base classes or aspects in AspectJ programs. The paper also reports on an empirical study that compares the cost and effectiveness of data-flow test criteria that are based on state variables with two control-flow criteria.MethodEffectiveness of the criteria was evaluated for various fault types. Cost-effectiveness of test suites that cover all state variable definition-use associations (DUAs) was evaluated for three coverage levels: 100%, 90%, and 80%.ResultsThe effort needed to obtain a test case that achieves data-flow coverage is higher than the effort needed to obtain a test case that covers a block or a branch in an advised class. Covering certain data flow associations requires more effort than for other types of data flow associations. The data-flow test criteria based on state variables of a base-class are in general more effective than control-flow criteria.ConclusionsOverall, it is cost-effective to obtain test suites at the 90% coverage level of data-flow criteria.     

Laboratory Visibility Studies of Directional Symbols used for Traffic Control Signals

Abstract

Three criteria are used to find the best of eight directional symbols suitable for traffic control signals: visibility when blurred, visibility at low contrast and identification in relation to acceptability. These are used instead of the more conventional field type criteria of recognition distance and reaction time. The results of the three experiments show that: 1. the rank order of performance with different symbols differs with the criterion used, 2. the blur variable, which is a relatively new visibility criterion, has proved successful in differentiating between symbols, and 3. visibility can be better for unconventional symbols than for the more conventional forms.