We describe problems associated with accessing data resources external to the application, which we term externalities, in replicated synchronous collaborative applications. Accessing externalities such as files, data...
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We describe problems associated with accessing data resources external to the application, which we term externalities, in replicated synchronous collaborative applications. Accessing externalities such as files, databases, network connections, environment variables, and the system clock is not as straightforward in replicated collaborative software as in single-user applications or centralized collaborative systems. We describe ad hoc solutions that add to development cost and complexity because the developer must program different behavior for different replicas. We introduce a novel general approach to accessing externalities uniformly in a replicated collaborative system. The approach uses a semireplicated architecture where the actual externality resides at a single location and is accessed via replicated proxies. This approach allows developers of replicated synchronous groupware to 1) use similar externality access mechanisms as in traditional single-user applications, and 2) program all replicas to execute the same behavior. We describe a general design for proxied access to read-only, write-only, and read-write externalities and discuss the tradeoffs of this semireplicated approach over full, literal replication and the class of applications to which this approach can be successfully applied. We also describe details of a prototype implementation of this approach within a replicated collaboration-transparency system, called Flexible JAMM (Java Applets Made Multiuser).
It is well known that vector-tenser notation is a compact and natural language for the mathematical formulation of continuum mechanics problems. Here we describe the application of vector technique to numerical simula...
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It is well known that vector-tenser notation is a compact and natural language for the mathematical formulation of continuum mechanics problems. Here we describe the application of vector technique to numerical simulation starting with a mathematical formulation. We provide an efficient numerical scheme and furnish an implementation as a computer program. As a result (in comparison with traditional "component" form), the two last steps are significantly simplified, especially for multidimensional problems with various boundary conditions in irregular geometries where nonorthogonal meshes are applied. Therefore, more attention can be focused on the physical nature of problems. Apart from the cleaner syntax, vector notation conserves the structure of traditional numerical algorithms and solves multidimensional problems with minimum additional programming effort. Complex practical applications of this technique are described as well. (C) 2001 Academic Press.
This paper describes how the U'DU decomposition method and sub-structuring algorithms can be implemented using object-oriented techniques. It is shown that this enables the algorithms to be implemented very concis...
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This paper describes how the U'DU decomposition method and sub-structuring algorithms can be implemented using object-oriented techniques. It is shown that this enables the algorithms to be implemented very concisely. Moreover, there is no increase in code complexity when the algorithms are extended to take account of sparsity. The sub-structuring, or domain decomposition algorithms are expressed in block matrix terms, and classes are used to represent each of these matrices. The solution processes are incorporated in a finite element program. The finite element program uses a distributed data structure, and this facilitates a straightforward interface between the finite element program and the mathematics. Moreover, the program possesses a clear control structure for responding to user changes to the finite element model. (C) 2001 Civil-Comp Ltd and Elsevier Science Ltd. All rights reserved.
The object-oriented paradigm in software engineering provides support for the construction of modular and reusable program components and is attractive for the design of large and complex distributed systems. Reachabi...
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The object-oriented paradigm in software engineering provides support for the construction of modular and reusable program components and is attractive for the design of large and complex distributed systems. Reachability analysis is an important and well-known tool for static analysis of critical properties in concurrent programs, such as deadlock freedom. It involves the systematic enumeration of all possible global states of program execution and provides the same level of assurance for properties of the synchronization structure in concurrent programs, such as formal verification. However, direct application of traditional reachability analysis to concurrent object-oriented programs has many problems, such as incomplete analysis for reusable classes (not safe) and increased computational complexity (not efficient). We have proposed a novel technique called apportioning, for safe and efficient reachability analysis of concurrent object-oriented programs, that is based upon a simple but powerful idea of classification of program analysis points as local (having influence within a class) and global (having possible influence outside a class). Given a program and a classification of its analysis points, reachability graphs are generated for 1) an abstract version of each class in the program having only local analysis points and 2) an abstract version of the whole program having only global analysis points. The error to be checked is decomposed into a number of subproperties, which are checked in the appropriate, reachability graphs. Different choices for the classification of analysis points, provide the flexibility to have many algorithms that are safe and efficient for different subclasses of programs. We have developed a number of apportioning-based algorithms, having different degrees of safety and efficiency. In this paper, we present the details of one of these algorithms, formally show its safety for an appropriate class of programs, and present experimental
An investigation of component-based approaches for software reuse is described. In the days when computer architecture was simpler and systems were developed by procedural languages or other paradigms, it was common t...
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An investigation of component-based approaches for software reuse is described. In the days when computer architecture was simpler and systems were developed by procedural languages or other paradigms, it was common that the functionality available within one system was also present in another system. However, these paradigms are not appropriate for surfacing components for developing distributed applications as defined by today's business requirements, and do not facilitate software reuse. It is envisaged that software reuse can be achieved through component-based development. This article discusses the characteristics of components and provides a brief study of the component systems of COM/DCOM, CORBA and Java RMI. An example is presented using Java RMI and develops keyboard functionality for the Web-aware version that matches the original 'green screen' application.
The authors' technique for process definition demonstrates practical value beyond direct project planning and risk mitigation: using object-oriented technology metaphors, it can express responsibilities and collab...
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The authors' technique for process definition demonstrates practical value beyond direct project planning and risk mitigation: using object-oriented technology metaphors, it can express responsibilities and collaborations among work units as classes. The technique yields a detailed Mark breakdown structure, accelerates development of more concise contrast language for follow-up work, improves level-of-effort estimates for future work, and enables continuous process improvement. The process definition technique also introduces team members to OOT principles and concepts.
The paper describes the structure of an environment for a design system based on a design plan, which represents a design process. The approach presented establishes a flexible structure, which improves and integrates...
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The paper describes the structure of an environment for a design system based on a design plan, which represents a design process. The approach presented establishes a flexible structure, which improves and integrates the usage of software tools available in the design process. Possible design plan topologies, the plan generation and exploitation issues are discussed. The structure of the prototype model has been realized in a relational database environment. The potentials of an object-oriented approach to design process planning are analysed, as well as the possible strategies for improving the prototype procedure. Proposals for structuring a design plan with objects and classes are presented.
This paper presents an extensible object model for gas turbine engine performance simulation. The extension method for gas path balancing is analyzed and a new design rationale is developed to overcome deficiencies of...
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This paper presents an extensible object model for gas turbine engine performance simulation. The extension method for gas path balancing is analyzed and a new design rationale is developed to overcome deficiencies of the traditional component-based object modeling method. A class framework implementing this rationale is described and the dynamic performance of a three-shaft gas turbine engine is simulated to evaluate the model's effectiveness. (C) 2000 Elsevier Science Ltd. All rights reserved.
The objectorientedprogramming technique can greatly improve the implementation efficiency, extendibility and ease of maintenance of large engineering software. In this paper, an object-oriented framework for impleme...
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The objectorientedprogramming technique can greatly improve the implementation efficiency, extendibility and ease of maintenance of large engineering software. In this paper, an object-oriented framework for implementing the finite element method is presented. The framework was designed to exploit the commonalties in the methodology between the numerous types of analysis, applied loads, constraints and equation solving algorithms so that duplication is minimized and software reuse is maximized when new capabilities are added to the software. Furthermore, the framework ensures that minimal or no modifications are required to previously implemented functions and classes when the software is extended. (C) 2001 Elsevier Science Ltd. All rights reserved.
This research work aims to develop an intelligent knowledge-based system that accomplishes an environment to assist inexperienced users to estimate the manufacturing cost modelling of a product at the conceptual desig...
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This research work aims to develop an intelligent knowledge-based system that accomplishes an environment to assist inexperienced users to estimate the manufacturing cost modelling of a product at the conceptual design stage of the product life cycle. Therefore, a quicker response to customers' expectations is generated. This paper discusses the development process of the proposed system for cost modelling of machining processes. Tt embodies a CAD solid modelling system, user interface, material selection, process/machine selection, and cost estimation techniques. The main function of the system, besides estimating the product cost, is to generate initial process planning includes generation and selection of machining processes, their sequence and their machining parameters. Therefore, the developed system differs from conventional product cost estimating systems, in that it is structured to support concurrent engineering. Manufacturing knowledge is represented by hybrid knowledge representation techniques, such as production rules, frames and objectoriented. To handle the uncertainty in cost estimation model that cannot be addressed by traditional analytical methods, a fuzzy logic-based knowledge representation is implemented in the developed system. Based on the analysis of product life cycle, the estimated cost included material, processing, machine set-up and non-productive costs. A case study is discussed and demonstrated to validate the proposed system. (C) 2001 Elsevier Science Ltd. All rights reserved.
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