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Semantics of Types for Mutable State
, 2004
"... Proofcarrying code (PCC) is a framework for mechanically verifying the safety of machine language programs. A program that is successfully verified by a PCC system is guaranteed to be safe to execute, but this safety guarantee is contingent upon the correctness of various trusted components. For in ..."
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Cited by 60 (4 self)
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Proofcarrying code (PCC) is a framework for mechanically verifying the safety of machine language programs. A program that is successfully verified by a PCC system is guaranteed to be safe to execute, but this safety guarantee is contingent upon the correctness of various trusted components. For instance, in traditional PCC systems the trusted computing base includes a large set of lowlevel typing rules. Foundational PCC systems seek to minimize the size of the trusted computing base. In particular, they eliminate the need to trust complex, lowlevel type systems by providing machinecheckable proofs of type soundness for real machine languages. In this thesis, I demonstrate the use of logical relations for proving the soundness of type systems for mutable state. Specifically, I focus on type systems that ensure the safe allocation, update, and reuse of memory. For each type in the language, I define logical relations that explain the meaning of the type in terms of the operational semantics of the language. Using this model of types, I prove each typing rule as a lemma. The major contribution is a model of System F with general references — that is, mutable cells that can hold values of any closed type including other references, functions, recursive types, and impredicative quantified types. The model is based on ideas from both possible worlds and the indexed model of Appel and McAllester. I show how the model of mutable references is encoded in higherorder logic. I also show how to construct an indexed possibleworlds model for a von Neumann machine. The latter is used in the Princeton Foundational PCC system to prove type safety for a fullfledged lowlevel typed assembly language. Finally, I present a semantic model for a region calculus that supports typeinvariant references as well as memory reuse. iii
A Stratified Semantics of General References Embeddable in HigherOrder Logic (Extended Abstract)
, 2002
"... Amal J. Ahmed Andrew W. Appel # Roberto Virga Princeton University {amal,appel,rvirga}@cs.princeton.edu Abstract We demonstrate a semantic model of general references  that is, mutable memory cells that may contain values of any (staticallychecked) closed type, including other references. Our mo ..."
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Cited by 33 (8 self)
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Amal J. Ahmed Andrew W. Appel # Roberto Virga Princeton University {amal,appel,rvirga}@cs.princeton.edu Abstract We demonstrate a semantic model of general references  that is, mutable memory cells that may contain values of any (staticallychecked) closed type, including other references. Our model is in terms of execution sequences on a von Neumann machine
Summary
, 2003
"... An important role in fuzzy logic and fuzzy control is played by linguistic descriptions, i.e. finite sets of IFTHEN rules. These rules often include socalled evaluating linguistic expressions – natural language expressions which characterize a position on an ordered scale, usually on a real interv ..."
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An important role in fuzzy logic and fuzzy control is played by linguistic descriptions, i.e. finite sets of IFTHEN rules. These rules often include socalled evaluating linguistic expressions – natural language expressions which characterize a position on an ordered scale, usually on a real interval. Examples of evaluating linguistic expressions are small, more or less medium, approximately 20 etc. Given a linguistic description of a process, situation, environment etc., and an observation, i.e. a value measured in some concrete situation, the task is to determine the conclusion by some plausible method. This thesis proposes a methodology for dealing with the abovedescribed situation and studies its properties. The basis for it is fuzzy logic in a narrow sense with evaluated syntax [27]. IFTHEN rules are understood as linguistically expressed logical implications. We consistently distinguished three levels of study – linguistic, syntactic and semantic. The meaning of evaluating linguistic expression is characterized on syntactic level by its intension and on semantic level by a class of its extensions.