ion and Model Checking Counter Example checking and predicate discovery Concrete System Verification Condition Initial Predicates Discovered predicates Property verified Abstract Counter−example Counter−example found Fig. 1. Predi ate Abstra tion Algorithm a veri ation ondition and the on rete system des ription it rst omputes an approximate abstra t model. This abstra t model is model he ked a...

s a f e t y : t h e o r e m p r o v e r f e e d b a c k Fig. 1. S heme of proving safety statements When a safe data abstra tion is obtained, veri ation of the model against a property an start. First, the abstra t data type and fun tion de nitions are inserted into the system spe i ation substituting the on rete de nitions of the original model. Next, the abstra t model together with the prope...

The verification problem for a system consisting of components can be decomposed into simpler subproblems for the components using assume-guarantee reasoning. However, such compositional reasoning requires user guidance to identify appropriate assumptions for components. In this paper, we propose an automated solution for discovering assumptions based on the L* algorithm for active learning of ...

It seems silly and impractical: to write a garbage collector (for a Prolog engine) in Prolog itself. However, there are at least three advantages in doing so: (1) one gets a runnable specification of the garbage collector, (2) it can enhance understanding of the algorithms involved without having to worry about gory pointer details, (3) the garbage collector written in Prolog can be used for de...

Fourier Transforms have been available for PureData for a long time. However they have never been applied to pixels, not ounting the possibility that someone onverted an image to sound in order to use [ t~℄ on it, whi h is fastidious and is still just a one-dimensional transform. This paper exposes the possibilities of using Fourier Transforms on whole images and on sequen es of them that enabl...

S hool performan e tables" { an alphabeti al list of se ondary s hools along with aggregates of their pupils' performan e in national test { have been published in Great Britain sin e 1992. inevitably the media have responded by publishing ranked \league tables". Despite on ern over the potentially divisive e e t of su h tables the urrent Labour government has ontinued to publish this informati...

We define the notion of critical set of an F-square, following the definition of critical set in latin squares, and then give critical sets for certain classes of F-squares. We also generalise certain results obtained for critical sets of latin squares, and look at minimal such sets. We show that critical sets of F-squares need to be studied as well as critical sets for latin squares as the tec...

Many modern systems show dynami hara teristi s in a sense that they hange their on guration dynami ally during run-time. In obje t-oriented systems, for example, the on guration of obje ts and their links hanges to re e t the state of systems. Unfortunately, few analysis te hniques address the dynami nature expli itly and, thus, there is a gap between analysis result and reality. That is, it is...

The stability of onstantoe ients semi-impli it s hemes for the hydrostati primitive equations and the fully elasti Euler equations in presen e of expli itly treated thermal residuals has been theoreti ally examined in the earlier literature, but only for the ase of a at terrain. This paper extends these analyses to the ase where an orography is present, in the shape of a uniform slope. It is sh...

Cost fun tions formulated in four-dimensional variational data assimilation (4D-Var) are nonsmooth in the presen e of dis ontinuous physi al pro esses (i.e., the presen e of \on-o " swit hes in NWP models). The adjoint model integration produ es values of subgradients, instead of gradients, of these ost fun tions with respe t to the model's ontrol variables at dis ontinuous points. Minimization...