A wide range of database applications manage information that varies over time. Many of the underlying database schemas of these were designed using one of the several versions of the Entity-Relationship (ER) model. I...
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ISBN:
(纸本)9781920682354
A wide range of database applications manage information that varies over time. Many of the underlying database schemas of these were designed using one of the several versions of the Entity-Relationship (ER) model. In the research community as well as in industry, it is common knowledge that the temporal aspects of the mini-world are pervasive and important, but are also difficult to capture using the ER model. Not surprisingly, several enhancements to the ER model have been proposed in an attempt to more naturally and elegantly support the modeling of temporal aspects of information. Common to most of the existing temporally extended ER models is that the semantics of the models are unclear. This problem is addressed in this paper by developing a formal semantics for the TIMEER model based on denotational semantics.
Denotational semantics is presented as a valuable theoretical tool, having many applications including language design, compiler generation and program analysis. In particular, a method is described for deriving a con...
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ISBN:
(纸本)0769509630
Denotational semantics is presented as a valuable theoretical tool, having many applications including language design, compiler generation and program analysis. In particular, a method is described for deriving a concise and useful functional representation of a program using a denotational definition of the source language's semantics. Our aim is to translate a given program into a compact functional representation to facilitate its evaluation on functional hardware. The λ-expressions are first translated into Turner's combinator code (see [7]). We choose to use a fixed set of combinators as the resulting code is more amenable to analysis and there are many inherent advantages such as lazy evaluation and once only evaluation of reducible sub-expressions. Semantic algebras relating to static semantics and the store algebra are "unfrozen" so they can be partially evaluated. The reduction machine that performs the evaluation includes simplification rules that allows a more compact functional representation (denotation) to be reached. If desired, some or all of the programs arguments can be supplied to produce a new denotation (result) using the same reduction machine.
We introduce a notion of higher-order parity automaton which extends to infinitary simply-typed λ-terms the traditional notion of parity tree automaton on infinitary ranked trees. Our main result is that the acceptan...
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ISBN:
(纸本)9781509030187
We introduce a notion of higher-order parity automaton which extends to infinitary simply-typed λ-terms the traditional notion of parity tree automaton on infinitary ranked trees. Our main result is that the acceptance of an infinitary λ-term by a higher-order parity automaton A is decidable, whenever the infinitary λ-term is generated by a finite and simply-typed λY-term. The decidability theorem is established by combining ideas coming from linear logic, from denotational semantics and from infinitary rewriting theory.
Representing the sharing and exchanging data withmachine-readable format allows cooperative taskautomation. In this paper we propose an XML Schemaand semantic based relational data translation approach,which aims at p...
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ISBN:
(纸本)0780379411
Representing the sharing and exchanging data withmachine-readable format allows cooperative taskautomation. In this paper we propose an XML Schemaand semantic based relational data translation approach,which aims at providing a coherent and meaningful viewof the relational data and enabling distributed users tocooperate on large data volumes online. We define adirected-graph data model as the common data model,present a key-based relational schema reversereconstruction arithmetic to capture the full structuresand semantic constraints in relational schema, andpropose a constraints-preserving mapping algorithm totranslate relational data into the global XMLrepresentations.
Predictive models are fundamental to engineering reliable software systems. However, designing conservative, computable approximations for the behavior of programs (static analyses) remains a difficult and error-prone...
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Predictive models are fundamental to engineering reliable software systems. However, designing conservative, computable approximations for the behavior of programs (static analyses) remains a difficult and error-prone process for modern high-level programminglanguages. What analysis designers need is a principled method for navigating the gap between semantics and analytic models: analysis designers need a method that tames the interaction of complex languages features such as higher-order functions, recursion, exceptions, continuations, objects and dynamic allocation. We contribute a systematic approach to program analysis that yields novel and transparently sound static analyses. Our approach relies on existing derivational techniques to transform high-level languagesemantics into low-level deterministic state-transition systems (with potentially infinite state spaces). We then perform a series of simple machine refactorings to obtain a sound, computable approximation, which takes the form of a non-deterministic state-transition systems with finite state spaces. The approach scales up uniformly to enable program analysis of realistic language features, including higher-order functions, tail calls, conditionals, side effects, exceptions, first-class continuations, and even garbage collection.
Formal methods advocate the crucial role played by the algebra of programs in specification and implementation of programs. Study leads to the conclusion that both the top-down approach (with denotational model as its...
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ISBN:
(纸本)9781509050826
Formal methods advocate the crucial role played by the algebra of programs in specification and implementation of programs. Study leads to the conclusion that both the top-down approach (with denotational model as its origin) and the bottom-up approach (a journey started from operational model) can meet in the middle with a program algebra. This paper proposes a new approach on linking theories of programming. Given a program algebra, we construct a test operator taking a test case and the testing program as its arguments. The operator yields a collection of observations of the test outcomes. The denotational model of a program can be derived as a binary relation which relates the test cases with their outcomes. An operational model is considered as consistent if its step relation is consistent with the algebraic semantics.
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