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Parallel Processing Letters 2001年第4期11卷 439-454页

作者： Chen, Yifeng Sanders, J.W. Department of Maths and Computer Science University of Leicester University Road Leicester LE1 7RH United Kingdom Programming Research Group Oxford University Computing Laboratory Parks Road Oxford OX1 3QD United Kingdom

This paper introduces a calculus of weakest specification for supporting reuse of established components in deriving a design (in the sense of formal methods). The weakest specifunction generalizes the notions of weakest pre-specification and weakest parallel environment;but instead of calculating the weakest required component of a target specification, it calculates the weakest specification function whose value refines the target when applied to an established component. In particular it overcomes the restriction of those other calculi to taking merely one required component at a time. The theory of specifunctions is applied to a new weakest-design calculus in the context of BSP. The calculus is based on the par-seq specifunction which involves two required components: it places one established component in parallel with one required component and the result in sequence with another required component to meet a given specification. A calculus is provided for the par-seq specifunction and it is applied to the derivation of a distributed BSP algorithm for greatest common divisor.

关键词： Parallel processing systems

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Consistent modeling of distributed mutual exclusion protocol using optimistic simulation

Consistent modeling of distributed mutual exclusion protocol...

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Workshop on Principles of Advanced and Distributed Simulation (PADS)

作者： M.Y.H. Low D.M. Nicol Programming Research Group Computing Laboratory University of Oxford UK Department of Computer Science Dartmouth College USA

ISBN: (纸本)076951104X

This paper discusses the problem of risk in optimistic simulation protocols, using as an example, simulation of a distributed mutual exclusion protocol with strong consistency properties. The simulation model is augmented to detect model inconsistency errors resulting from risky optimistic simulation. While the model runs sequentially without consistency errors, errors occur when the model is executed in parallel optimistically. Some of the errors entirely violate the fundamental mutual exclusion properties of the model itself. To address this problem, we extend the optimistic simulation library to eliminate these inconsistencies. We discuss the details of these extensions and the performance tradeoff for adding them.

关键词： Protocols Computational modeling Libraries Hazards computer simulation Laboratories computer science Educational institutions computer errors Parallel processing

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Aspect-oriented frameworks: The design of adaptable operating systems

Aspect-oriented frameworks: The design of adaptable operatin...

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2000 Conference on Object-Oriented programming, Systems, Languages, and Applications, OOPSLA 2000

作者： Netinant, P. Constantinides, C.A. Elrad, T. Fayad, M.E. Concurrent Research Group Computer Science Department Illinois Institute of Technology Chicago IL United States Department of Computer Science and Engineering University of Nebraska - Lincoln Lincoln NE United States

ISBN: (纸本)1581133073

With software systems such as operating systems, the interaction of their components becomes more complex. This interaction may limit reusability, adaptability, and make it difficult to validate the design and correctness of the system. As a result, re-engineering of these systems might be inevitable to meet future requirements. There is a general feeling that OOP promotes reuse and expandability by its very nature. This is a misconception as none of these issues is enforced. Rather, a software system must be specifically designed for reuse, expandability, and adaptability [4]. Operating systems are dominated in many aspects. Supporting separation of concerns and aspectual decomposition in the design of operating systems provides a number of benefits such as reusability, expandability, adaptability and reconfigurability. However, such support is difficult to accomplish. Aspect-Oriented programming (AOP) [7] is a paradigm proposal that aims at separating components and aspects from the early stages of the software life cycle, and combines them together at the implementation phase. Besides, Aspect-Oriented programming promotes the separation of the different aspects of components in the system into their natural form. However, Aspect-Oriented software engineering can be supported well if there is an operating system, which is built based on an aspect-oriented design. Therefore aspects can be created in applications, reused and adapted from the aspects provided by the operating systems. Object-Oriented Operating Systems treat aspects, components, and layers as a two dimensional models, which is not a good design model. Aspects in the operating system cannot be captured in the design and implementation. Two-dimensional models lead to inflexibility, limit possibilities for reuse and adaptability, and make it hard to understand and modify. The poster will show an Aspect-Oriented Framework [1, 8], which simplifies system design by expressing its design at a higher level of

关键词： Reusability

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Designing an Aspect-Oriented Framework in an Object-Oriented Environment

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ACM Computing Surveys 2000年第1ES期32卷 41-41页

作者： Constantinides, Constantinos A. Bader, Atef Elrad, Tzilla H. Netinant, P. Fayad, Mohamed E. Concurrent Programming Research Group Department of Computer Science Illinois Institute of Technology United States University of Nebraska Lincoln United States

Separation of concerns is at the heart of software development, and although its benefits have been well established, the core problem remains how to achieve it. For complex software systems the solution is still debatable and it is a major research area. Object Oriented programming (OOP) works well only if the problem at hand can be described with relatively simple interface among objects. Unfortunately, this is not the case when we move from sequential programming to concurrent and distributed programming. The September 1993 CACM issue was devoted to the problematic marriage between OOP and Concurrency [Cohen 93]. Since then, numerous workshops, articles and books have attempt to tackle the problem. The core complexity is that concurrent and distributed systems manifest over more than one dimension. Features such as scheduling, synchronization, fault tolerance, security, testing and verifications are all expressed in such a way that they tend to cut across different objects. Hence, simple object interfaces are violated and the traditional OOP benefits no longer hold. One of the current attempts to resolve this issue is the Aspect Oriented Software Architecture. To address this multi-dimensional structure of concurrent systems we distinguish between components and aspects. Aspects are defined as properties of a system that do not necessarily align with the system’s functional components but tend to cut across functional components, increasing their interdependencies, and thus affecting the quality of the software. Although not bound to OOP, Aspect-Oriented programming (AOP) is a paradigm proposal that retains the advantages of OOP and aims at achieving a better separation of concerns. In this paper we provide an assessment of AOP and we discuss the architecture of an aspect-oriented framework. The goals of our proposal is to achieve an improved separation of concerns in both design, and implementation, to provide adaptability, and to support the complex interaction

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Generalised folds for nested datatypes

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Formal Aspects of Computing 1999年第2期11卷 200-222页

作者： Bird, Richard Paterson, Ross Programming Research Group Oxford University Oxford United Kingdom Department of Computer Science City University London United Kingdom Programming Research Group Oxford University Wolfson Building Parks Road Oxford OX1 3QD United Kingdom

Nested datatypes generalise regular datatypes in much the same way that context-free languages generalise regular ones. Although the categorical semantics of nested types turns out to be similar to the regular case, the fold functions are more limited because they can only describe natural transformations. Practical considerations therefore dictate the introduction of a generalised fold function in which this limitation can be overcome. In the paper we show how to construct generalised folds systematically for each nested datatype, and show that they possess a uniqueness property analogous to that of ordinary folds. As a consequence, generalised folds satisfy fusion properties similar to those developed for regular datatypes. Such properties form the core of an effective calculational theory of inductive datatypes.

关键词： Keywords: Functional programming Program construction

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A Minimal Graphical User Interface for the Jape Proof Calculator

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Formal Aspects of Computing 1999年第3期11卷 244-271页

作者： Bornat, Richard Sufrin, Bernard Programming Research Group University of Oxford Oxford United Kingdom Department of Computer Science Queen Mary and Westfield College University of London London E1 4NS United Kingdom

GUI design isn't simply a matter of putting a nice front-end on a capable program. It requires thought about the way in which people might be expected to use a system, and investigation of the ways that they actually use it. Jape's GUI has been designed to be as simple as possible, so that it will not get in the way of the business of proof. It is designed to be minimal in the information that it displays and the gestures that it requires from the user. In this paper we introduce and give a rationale for the design of Jape's user interface, then note some of its drawbacks.

关键词： GUI proof Proof calculator

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De Bruijn notation as a nested datatype

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Journal of Functional programming 1999年第1期9卷 77-91页

作者： Bird, Richard S. Paterson, Ross Programming Research Group Oxford University Wolfson Building Oxford OX1 3QD Parks Road United Kingdom Department of Computer Science City University London EC1V 0HB Northampton Square United Kingdom

de Bruijn notation is a coding of lambda terms in which each occurrence of a bound variable x is replaced by a natural number, indicating the 'distance' from the occurrence to the abstraction that introduced x. One might suppose that in any datatype for representing de Bruijn terms, the distance restriction on numbers would have to maintained as an explicit datatype invariant. However, by using a nested (or non-regular) datatype, we can define a representation in which all terms are well-formed, so that the invariant is enforced automatically by the type system. programming with nested types is only a little more difficult than programming with regular types, provided we stick to well-established structuring techniques. These involve expressing inductively defined functions in terms of an appropriate fold function for the type, and using fusion laws to establish their properties. In particular, the definition of lambda abstraction and beta reduction is particularly simple, and the proof of their associated properties is entirely mechanical.

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Nested datatypes 4th

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4th International Conference on Mathematics of Program Construction, MPC 1998

作者： Bird, Richard Meertens, Lambert Programming Research Group Oxford University Wolfson Building Parks Road OxfordOX1 3QD United Kingdom CWI and Department of Computer Science Utrecht University P.O. Box 94079 AmsterdamGB1090 Netherlands

ISBN: (纸本)3540645918

A nested datatype, also known as a non-regular datatype, is a parametrised datatype whose declaration involves different instances of the accompanying type parameters. Nested datatypes have been mostly ignored in functional programming until recently, but they are turning out to be both theoretically important and useful in practice. The aim of this paper is to suggest a functorial semantics for such datatypes, with an associated calculational theory that mirrors and extends the standard theory for regular datatypes. Though elegant and generic, the proposed approach appears more limited than one would like, and some of the limitations are discussed. © Springer-Verlag Berlin Heidelberg 1998.

关键词： Functional programming

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Software cost estimation using economic production models

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Journal of Management Information Systems 1998年第1期15卷 143-163页

作者： Hu, Q. Plant, R.T. Hertz, D.B. Dept. of Decis. and Info. Systems Florida Atlantic University United States University of Miami FL United States Dept. of Comp. Information Systems University of Miami Coral Gables FL United States University of Liverpool United Kingdom Programming Research Group Oxford University Wadham College Oxford United Kingdom Department of Computer Science Univ. of Wolverhampton in England Templeton College Oxford United Kingdom Dept. of Comp. Information Systems University of Miami United States Columbia University CEO Identification Technol. Intl. Inc. United States McKinsey and Co. New York City NY United States

One of the major difficulties in controlling software development project cost overruns and schedule delays has been developing practical and accurate software cost models. Software development could be modeled as an economic production process and we therefore propose a theoretical approach to software cost modeling. Specifically, we present the Minimum Software Cost Model (MSCM), derived from economic production theory and systems optimization. The MSCM model is compared with other widely used software cost models, such as COCOMO and SLIM, on the basis of goodness of fit and quality of estimation using software project data sets available in the literature. Judged by both criteria, the MSCM model is comparable to, if not better than, the SLIM, and significantly better than the rest of the models. In addition, the MSCM model provides some insights about the behavior of software development processes and environment, which could be used to formulate guidelines for better software project management polic es and practices.

关键词： Economic production theory Software cost estimation Software cost models Software production Software project management

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Developing a prototype concurrent design tool for composite topside structures

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NAVAL ENGINEERS JOURNAL 1997年第3期109卷 279-290页

作者： Dirlik, S Hambric, S Azarm, S Marquardt, M Hellman, A Bartlett, S Castelli, V Steve Dirlik:began his career at the Naval Surface Warfare Center Carderock Division in 1981 as an aerospace engineer co-op student. He completed his bachelor of science degree in aeropace and ocean engineering from Virginia Polytechnic Institute and State University in 1985 and his master of science degree in aerospace engineering from the University of Maryland in 1990. Mr. Dirlik recently completed a master of science program in applied physics at The Johns Hopins University and currently works in the Radar Cross Section and Target Physics Branch of the Signatures Directorate at the Naval Surface Warfare Center Corderoke Division. He has worked on Navy low observable programs since 1990. Stephen Hambric:is a research associate at the Applied Research Laboratory at The Pennsylvania State University. He received his B. S. and M.S. degree in mechanical engineering from Virginia Polytechnic Institute and State University and his D. Sc. in mechnical engineering from the George Washington University. He has worked on several computer aided multidiscikplinary design and optimization projects over the years including an automated propeller design system and a structural acoustic optimization capability. Dr. Shpour Azarm:is currently working as an associate professor with the Design and Manufacturing Group of the Department of Mechanical Engineering at the University of maryland at College Park. Dr Azarm's expertise is in the areas of optimization-based designed and concurrent design and optimization of multidisciplinary systems. He was a consultant at Black & Decker Corporation (summer 1996) and worked as a Navy senior summer faculty fellow (summer 1995) and a NASA summer faculty fellow (summer 1994). He was a visiting scientist at NASA Langley Research Center for Multidisciplinary Analysis and Applied Structural Optimzatiom at the University of Siegen in Germany (spring 1992) and the Design Institute of the Technical University of Denmark (summer 1990). Dr Azarm was an associate technical editor of the ASME Jour

A prototype concurrent engineering tool has been developed for the preliminary design of composite topside structures for modern navy warships. This tool, named GELS for the concurrent Engineering of Layered Structures, provides designers with an immediate assessment of the impacts of their decisions on several disciplines which are important to the performance of a modern naval topside structure, including electromagnetic interference effects (EMI), radar cross section (RCS), structural integrity, cost, and weight. Preliminary analysis modules in each of these disciplines are integrated to operate from a common set of design variables and a common materials database. Performance in each discipline and an overall fitness function for the concept are then evaluated. A graphical user interface (GUI) is used to define requirements and to display the results from the technical analysis modules. Optimization techniques, including feasible sequential quadratic programming (FSQP) and exhaustive search are used to modify the design variables to satisfy all requirements simultaneously. The development of this tool, the technical modules, and their integration are discussed noting the decisions and compromises required to develop and integrate the modules into a prototype conceptual design tool.

关键词： Warships

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