25,771 research outputs found
Integrated Modeling and Verification of Real-Time Systems through Multiple Paradigms
Complex systems typically have many different parts and facets, with
different characteristics. In a multi-paradigm approach to modeling, formalisms
with different natures are used in combination to describe complementary parts
and aspects of the system. This can have a beneficial impact on the modeling
activity, as different paradigms an be better suited to describe different
aspects of the system. While each paradigm provides a different view on the
many facets of the system, it is of paramount importance that a coherent
comprehensive model emerges from the combination of the various partial
descriptions. In this paper we present a technique to model different aspects
of the same system with different formalisms, while keeping the various models
tightly integrated with one another. In addition, our approach leverages the
flexibility provided by a bounded satisfiability checker to encode the
verification problem of the integrated model in the propositional
satisfiability (SAT) problem; this allows users to carry out formal
verification activities both on the whole model and on parts thereof. The
effectiveness of the approach is illustrated through the example of a
monitoring system.Comment: 27 page
Who watches the watchers: Validating the ProB Validation Tool
Over the years, ProB has moved from a tool that complemented proving, to a
development environment that is now sometimes used instead of proving for
applications, such as exhaustive model checking or data validation. This has
led to much more stringent requirements on the integrity of ProB. In this paper
we present a summary of our validation efforts for ProB, in particular within
the context of the norm EN 50128 and safety critical applications in the
railway domain.Comment: In Proceedings F-IDE 2014, arXiv:1404.578
ADsafety: Type-Based Verification of JavaScript Sandboxing
Web sites routinely incorporate JavaScript programs from several sources into
a single page. These sources must be protected from one another, which requires
robust sandboxing. The many entry-points of sandboxes and the subtleties of
JavaScript demand robust verification of the actual sandbox source. We use a
novel type system for JavaScript to encode and verify sandboxing properties.
The resulting verifier is lightweight and efficient, and operates on actual
source. We demonstrate the effectiveness of our technique by applying it to
ADsafe, which revealed several bugs and other weaknesses.Comment: in Proceedings of the USENIX Security Symposium (2011
Modeling the Elastic Energy of Alloys: Potential Pitfalls of Continuum Treatments
Some issues that arise when modeling elastic energy for binary alloys are
discussed within the context of a Keating model and density functional
calculations. The Keating model is based on atomistic modeling of elastic
interactions in binary alloy using harmonic springs with species dependent
equilibrium lengths. It is demonstrated that the continuum limit for the strain
field are the usual equations of linear elasticity for alloys and that they
correctly capture the coarse-grained displacement field. In addition, it is
established that Euler-Lagrange equation of the continuum limit of the elastic
energy will yield the same strain field equation. However, a direct calculation
of the elastic energy of the atomistic model reveals that the continuum
expression for the elastic energy is both qualitatively and quantitatively
incorrect. This is because it does not take atomistic scale compositional
non-uniformity into account. Importantly, we also shows that finely mixed
alloys tend to have more elastic energy than segregated systems, which is the
opposite of predictions by some continuum theories. It is also shown that for
strained thin films the traditionally used effective misfit for alloys
systematically underestimate the strain energy. In some models, this drawback
is handled by including an elastic contribution to the enthalpy of mixing which
is characterized in terms of the continuum concentration. The direct
calculation of the atomistic model reveals that this approach suffers serious
difficulties. It is demonstrated that elastic contribution to the enthalpy of
mixing is non-isotropic and scale dependent. It also shown that such effects
are present in density-functional theory calculations for the Si/Ge and Ag/Pt
systems. This work demonstrates that it is critical to include the microscopic
arrangements in any elastic model to achieve even qualitatively correct
behavior
Checking the fact-checkers in 2008: predicting political ad scrutiny and assessing consistency
Which types of political ads are most likely to draw criticism from fact-checkers? Are fact-checkers consistent in their evaluations of political ads? Examining general election television ads from the 2008 U.S. presidential race, and based upon the evaluations of FactCheck.org, PolitiFact.com, and the Washington Post's Fact Checker, this study demonstrates it was the attack ads from candidates that were most likely to draw scrutiny from the fact-checkers. Most importantly, a high level of agreement between the fact-checkers indicates their success at selecting political claims that can be consistently evaluated. While political advertisers are increasingly using evidence to support their claims, what may be more critical in drawing evaluations from fact-checkers is the verifiability of a claim. The implications of consistent fact-checking on the public, political actors, journalism and democracy are discussed. With the revelation that fact-checking can be consistently practiced, localized efforts at fact-checking need encouragement, particularly as political TV ads increasingly drown out other potential sources of information for the public and increasingly are used in downballot races, local initiatives, referendums and judicial races
Improving a Modular Verification Technique for Aspect Oriented Programming
As aspect oriented software becomes more popular, there will be more demand for a method of verifying the correctness of the programs. This paper tries to address the verification issue by improving a modular verification technique proposed by Krisnamuhrti et al. The technique has the problem that it can not handle every aspect, which may result in a false awnser. By checking the type of the aspect in advance we can prevent this behavior. The proposed solution also improves some other issues regarding the model-checker
- …