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Will Informatics be able to Justify the Construction of Large Computer Based Systems?
, 2001
"... The present article addresses correct construction and functioning of large computer based systems. In view of so many annoying and dangerous system misbehaviors we want to ask: Can informaticians righteously be accounted for incorrectness of systems, will they be able to justify systems to work cor ..."
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The present article addresses correct construction and functioning of large computer based systems. In view of so many annoying and dangerous system misbehaviors we want to ask: Can informaticians righteously be accounted for incorrectness of systems, will they be able to justify systems to work correctly as intended? We understand the word justification in this sense, i.e., for the design of computer based systems, the formulation of mathematical models of information flows, and the construction of controlling software to be such that the expected system effects, the absence of internal failures, and the robustness towards misuses and malicious external attacks are foreseeable as logical consequences of the models.
Generic Compilation Schemes for Simple Programming Constructs
, 1999
"... datatype Expr and an evaluation function eval ( 77 ) then define syntax and semantics of expressions where the state (SState) is defined as a mapping from identifiers to values. 77 %  semantics of expressions  eval(e:Expr)(s:SState) : RECURSIVE Value = CASES e OF const(val) : val, varid(name) ..."
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datatype Expr and an evaluation function eval ( 77 ) then define syntax and semantics of expressions where the state (SState) is defined as a mapping from identifiers to values. 77 %  semantics of expressions  eval(e:Expr)(s:SState) : RECURSIVE Value = CASES e OF const(val) : val, varid(name) : s(name), unopr(op,arg) : MUnop(op)(eval(arg)(s)), binopr(op,left,right) : MBinop(op)(eval(left)(s), eval(right)(s)) ENDCASES MEASURE e BY !! Since boolean expressions are treated in a similar way as expressions, we do not define them explicitly but instead suppose that an (uninterpreted) type BExp together with an evaluation function eval bexp : [BExp ? [SState ? bool]] is given. Syntax and semantics of statements are defined by importing the generic theories for simple statements and control structures: %  import syntax and semantics of simple statements IMPORTING simplestatements[VarId, Expr, Value, eval] %  import syntax and semantics of control structures IMPORTING ctrlstruc[B...
From Algebraic Semantics to Denotational Semantics for Verilog ∗
"... This paper considers how the algebraic semantics for Verilog relates with its denotational semantics. Our approach is to derive the denotational semantics from the algebraic semantics. We first present the algebraic laws for Verilog. Every program can be expressed as a guarded choice that can model ..."
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This paper considers how the algebraic semantics for Verilog relates with its denotational semantics. Our approach is to derive the denotational semantics from the algebraic semantics. We first present the algebraic laws for Verilog. Every program can be expressed as a guarded choice that can model the execution of a program. In order to investigate the parallel expansion laws, a sequence is introduced, which indicates the instantaneous action is due to which exact parallel component. A normal form is defined for each program by using the locality sequence. We provide a strategy for deriving the denotational semantics based on the algebraic normal form. Using the strategy, the denotational semantics for every program can be calculated. Program equivalence can also be explored by using the derived denotational semantics. 1
Under consideration for publication in Formal Aspects of Computing The Variety of Variables in Automated RealTime Refinement
, 2002
"... Keywords: Computeraided programming; Program refinement theory; Realtime programming ..."
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Keywords: Computeraided programming; Program refinement theory; Realtime programming
Refining Exceptions Using King and Morgan’s exit Construct ∗
, 2002
"... Note: Most SVRC technical reports are available via anonymous ftp, from svrc.it.uq.edu.au in the directory /pub/techreports. Abstracts and compressed postscript files are available ..."
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Note: Most SVRC technical reports are available via anonymous ftp, from svrc.it.uq.edu.au in the directory /pub/techreports. Abstracts and compressed postscript files are available
Verifying Emulation of Legacy Mission Computer Systems
"... Abstract. Processor obsolescence is a serious maintenance problem for longlived embedded control systems. A practical solution is to interpose an emulator program between the ‘legacy ’ software and a replacement processor, so that the old code can be reused on the new machine. Unfortunately, no ver ..."
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Abstract. Processor obsolescence is a serious maintenance problem for longlived embedded control systems. A practical solution is to interpose an emulator program between the ‘legacy ’ software and a replacement processor, so that the old code can be reused on the new machine. Unfortunately, no verification techniques exist for proving that the resulting system preserves the original system’s functional and timing behaviour. A particular challenge is that processor emulation mixes both legacy assembly code and new highlevel language software patches. Nevertheless, we show that a formalism previously used for analysing program compilation, coupled with an understanding of the legacy software architecture, can be used to verify key aspects of an emulated control system. 1
Under consideration for publication in Formal Aspects of Computing Linear Approximation of ExecutionTime Constraints
"... Abstract. This paper defines an algorithm for predicting worstcase and bestcase execution times, and determining executiontime constraints of controlflow paths through realtime programs using their partial correctness semantics. The algorithm produces a linear approximation of path traversal co ..."
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Abstract. This paper defines an algorithm for predicting worstcase and bestcase execution times, and determining executiontime constraints of controlflow paths through realtime programs using their partial correctness semantics. The algorithm produces a linear approximation of path traversal conditions, worstcase and bestcase execution times and strongest postconditions for timed paths in abstract realtime programs. Also shown are techniques for determining the set of controlflow paths with decidable worstcase and bestcase execution times. The approach is based on a weakest liberal precondition semantics and relies on supremum and infimum calculations similar to standard computations from linear programming and Presburger arithmetic. The methodology is applicable to any executable language with a predicate transformer semantics and hence provides a verification basis for both high level language and assembly code executiontime analysis. Keywords: Realtime program analysis; Controlflow analysis; Timing prediction; Worstcase and bestcase execution times; Automatic constraint determination.
Class Refinement for Sequential Java
"... This extended abstract describes progress in an ongoing project on refinement calculus for sequential Java. Predicate transformer semantics is being used to validate correctnesspreserving transformations for use in program development, verification, design refactoring, and compilation. We focus her ..."
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This extended abstract describes progress in an ongoing project on refinement calculus for sequential Java. Predicate transformer semantics is being used to validate correctnesspreserving transformations for use in program development, verification, design refactoring, and compilation. We focus here on the semantics and its application in showing soundness of forward simulation for class refinement, the foundation of behavioral subclassing. This section is an overview of project objectives and recent progress. Section 2 addresses the language and its semantics. Section 3 discusses class refinement, Section 4 presents our ideas for future work.
A Hidden Approach to Program Behavior, Translation and Optimization
"... A user will perceive a compiler as correct if he or she cannot visibly distinguish between the behavior of a program interpreted in the source language semantics and the behavior of the compiled version of the same program. This allows to use the visible behavior of a program as a correctness argume ..."
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A user will perceive a compiler as correct if he or she cannot visibly distinguish between the behavior of a program interpreted in the source language semantics and the behavior of the compiled version of the same program. This allows to use the visible behavior of a program as a correctness argument for program translation as well as optimization.