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The Effects of
 Artificial Sources of Water on Rangeland Biodiversity. Environment Australia and CSIRO
, 1997
"... “Turing hoped that his abstractedpapertape model was so simple, so transparent and well defined, that it would not depend on any assumptions about physics that could conceivably be falsified, and therefore that it could become the basis of an abstract theory of computation that was independent of ..."
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Cited by 9 (5 self)
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“Turing hoped that his abstractedpapertape model was so simple, so transparent and well defined, that it would not depend on any assumptions about physics that could conceivably be falsified, and therefore that it could become the basis of an abstract theory of computation that was independent of the underlying physics. ‘He thought, ’ as Feynman once put it, ‘that he understood paper. ’ But he was mistaken. Real, quantummechanical paper is wildly different from the abstract stuff that the Turing machine uses. The Turing machine is entirely classical...”
Dynamic Enforcement of Knowledgebased Security Policies
"... Abstract—This paper explores the idea of knowledgebased security policies, which are used to decide whether to answer a query over secret data based on an estimation of the querier’s (possibly increased) knowledge given the result. Limiting knowledge is the goal of existing information release poli ..."
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Abstract—This paper explores the idea of knowledgebased security policies, which are used to decide whether to answer a query over secret data based on an estimation of the querier’s (possibly increased) knowledge given the result. Limiting knowledge is the goal of existing information release policies that employ mechanisms such as noising, anonymization, and redaction. Knowledgebased policies are more general: they increase flexibility by not fixing the means to restrict information flow. We enforce a knowledgebased policy by explicitly tracking a model of a querier’s belief about secret data, represented as a probability distribution. We then deny any query that could increase knowledge above a given threshold. We implement query analysis and belief tracking via abstract interpretation using a novel domain we call probabilistic polyhedra, whose design permits trading off precision with performance while ensuring estimates of a querier’s knowledge are sound. Experiments with our implementation show that several useful queries can be handled efficiently, and performance scales far better than would more standard implementations of probabilistic computation based on sampling. I.
Probabilistic πCalculus and Event Structures
"... This paper proposes two semantics of a probabilistic variant of the πcalculus: an interleaving semantics in terms of Segala automata and a true concurrent semantics, in terms of probabilistic event structures. The key technical point is a use of types to identify a good class of nondeterministic p ..."
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Cited by 2 (2 self)
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This paper proposes two semantics of a probabilistic variant of the πcalculus: an interleaving semantics in terms of Segala automata and a true concurrent semantics, in terms of probabilistic event structures. The key technical point is a use of types to identify a good class of nondeterministic probabilistic behaviours which can preserve a compositionality of the parallel operator in the event structures and the calculus. We show an operational correspondence between the two semantics. This allows us to prove a “probabilistic confluence” result, which generalises the confluence of the linearly typed πcalculus.
On probabilistic coherence spaces
, 2008
"... We introduce a probabilistic version of coherence spaces and show that these objects provide a model of linear logic. We build a model of the pure lambdacalculus in this setting and show how to interpret a probabilistic version of the functional language PCF. We give a probabilistic interpretation ..."
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We introduce a probabilistic version of coherence spaces and show that these objects provide a model of linear logic. We build a model of the pure lambdacalculus in this setting and show how to interpret a probabilistic version of the functional language PCF. We give a probabilistic interpretation of the semantics of probabilistic PCF closed terms of ground type.
Under consideration for publication in Math. Struct. in Comp. Science Reversible Combinatory Logic
, 2006
"... The λcalculus is destructive: its main computational mechanism – beta reduction – destroys the redex and makes it thus impossible to replay the computational steps. Combinatory logic is a variant of the λcalculus which maintains irreversibility. Recently, reversible computational models have been ..."
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The λcalculus is destructive: its main computational mechanism – beta reduction – destroys the redex and makes it thus impossible to replay the computational steps. Combinatory logic is a variant of the λcalculus which maintains irreversibility. Recently, reversible computational models have been studied mainly in the context of quantum computation, as (without measurements) quantum physics is inherently reversible. However, reversibility also changes fundamentally the semantical framework in which classical computation has to be investigated. We describe an implementation of classical combinatory logic into a reversible calculus for which we present an algebraic model based on a generalisation of the notion of group. 1.