21,629 research outputs found
The Budget-Constrained Functional Dependency
Armstrong's axioms of functional dependency form a well-known logical system
that captures properties of functional dependencies between sets of database
attributes. This article assumes that there are costs associated with
attributes and proposes an extension of Armstrong's system for reasoning about
budget-constrained functional dependencies in such a setting.
The main technical result of this article is the completeness theorem for the
proposed logical system. Although the proposed axioms are obtained by just
adding cost subscript to the original Armstrong's axioms, the proof of the
completeness for the proposed system is significantly more complicated than
that for the Armstrong's system
Program Verification of Numerical Computation
These notes outline a formal method for program verification of numerical
computation. It forms the basis of the software package VPC in its initial
phase of development. Much of the style of presentation is in the form of notes
that outline the definitions and rules upon which VPC is based. The initial
motivation of this project was to address some practical issues of computation,
especially of numerically intensive programs that are commonplace in computer
models. The project evolved into a wider area for program construction as
proofs leading to a model of inference in a more general sense. Some basic
results of machine arithmetic are derived as a demonstration of VPC
Combining Graph-Based and Deduction-Based Information-Flow Analysis
Information flow control (IFC) is a category of techniques for
ensuring system security by enforcing information flow properties such as
non-interference. Established IFC techniques range from fully automatic
approaches with much over-approximation to approaches with high pre-
cision but potentially laborious user interaction. A noteworthy approach
mitigating the weaknesses of both automatic and interactive IFC tech-
niques is the hybrid approach, developed by Küsters et al., which – how-
ever – is based on program modifications and still requires a significant
amount of user interaction.
In this paper, we present a combined approach that works without any
program modifications. It minimizes potential user interactions by apply-
ing a dependency-graph-based information-flow analysis first. Based on
over-approximations, this step potentially generates false positives. Pre-
cise non-interference proofs are achieved by applying a deductive theorem
prover with a specialized information-flow calculus for checking that no
path from a secret input to a public output exists. Both tools are fully
integrated into a combined approach, which is evaluated on a case study,
demonstrating the feasibility of automatic and precise non-interference
proofs for complex programs
A static analysis for quantifying information flow in a simple imperative language
We propose an approach to quantify interference in a simple imperative language that includes a looping construct. In this paper we focus on a particular case of this definition of interference: leakage of information from private variables to public ones via a Trojan Horse attack. We quantify leakage in terms of Shannon's information theory and we motivate our definition by proving a result relating this definition of leakage and the classical notion of programming language interference. The major contribution of the paper is a quantitative static analysis based on this definition for such a language. The analysis uses some non-trivial information theory results like Fano's inequality and L1 inequalities to provide reasonable bounds for conditional statements. While-loops are handled by integrating a qualitative flow-sensitive dependency analysis into the quantitative analysis
Automatic instantiation of abstract tests on specific configurations for large critical control systems
Computer-based control systems have grown in size, complexity, distribution
and criticality. In this paper a methodology is presented to perform an
abstract testing of such large control systems in an efficient way: an abstract
test is specified directly from system functional requirements and has to be
instantiated in more test runs to cover a specific configuration, comprising
any number of control entities (sensors, actuators and logic processes). Such a
process is usually performed by hand for each installation of the control
system, requiring a considerable time effort and being an error prone
verification activity. To automate a safe passage from abstract tests, related
to the so called generic software application, to any specific installation, an
algorithm is provided, starting from a reference architecture and a state-based
behavioural model of the control software. The presented approach has been
applied to a railway interlocking system, demonstrating its feasibility and
effectiveness in several years of testing experience
Epistemic Logic for Communication Chains
The paper considers epistemic properties of linear communication chains. It
describes a sound and complete logical system that, in addition to the standard
axioms of S5 in a multi-modal language, contains two non-trivial axioms that
capture the linear structure of communication chains.Comment: 7 pages, Contributed talk at TARK 2013 (arXiv:1310.6382)
http://www.tark.or
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