Since the mid-1970s, and with the development of each new programming paradigm there has been an increasing interest in exceptions and the benefits of exception handling. With the move towards programming for ever mor...
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Since the mid-1970s, and with the development of each new programming paradigm there has been an increasing interest in exceptions and the benefits of exception handling. With the move towards programming for ever more complex architectures, understanding basic facilities such as exception handling as an aid to improving program reliability, robustness and comprehensibility has become much more important. Interest has sparked the production of many papers both theoretical and practical, each giving a view of exceptions and exception handling from a different standpoint. In an effort to provide a means of classifying exception handling models which may be encountered, a taxonomy is presented in this paper. As the taxonomy is developed some of the concepts of exception handling are introduced and discussed. The taxonomy is applied to a number of exception handling models in some contemporary programming languages and some observations and conclusions offered.
The concept of anti-link is defined, and useful equivalence-preserving operations on propositional formulas based on anti-links are introduced. These operations eliminate a potentially large number of subsumed paths i...
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A formal framework for a calculus of real-time systems is presented. Specifications and program statements are combined into a single language called TAM (the Temporal Agent Model), that allows the user to express bot...
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A major limitation of the boundary element method (BEM) for the solution of electrical potential problems is the long computational time required. However, a large portion of the calculations involved can be viewed as...
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A major limitation of the boundary element method (BEM) for the solution of electrical potential problems is the long computational time required. However, a large portion of the calculations involved can be viewed as being parallel in nature and can therefore be computed concurrently. This paper makes an effort to increase the efficiency of the BEM process using transputer-based multiprocessor computing techniques. The algorithms developed may equally well be applied to any multiprocessor system. The application selected to demonstrate the technique is the solution of an electrostatic problem governed by a two-dimensional Laplace equation. A parallel algorithm for problem setup and field extraction using BEM is designed and implemented on a transputer array. Special attention is directed to the utilization of the parallel processors to achieve maximum efficiency. The analysis in this work concentrates on the communication strategies for passing data between processors as well as a consideration of the workload attributed to each processor. The parallel algorithms were implemented using 3L Parallel Fortran;however, the choice of topology for the overall BEM implementation was limited by the fact that certain parts of the algorithm could only utilize a pipeline configuration of processors. Comprehensive results for the parallel BEM algorithm are given and they are encouraging, indicating that parallel processing has much to offer when applied to the boundary element method.
A major limitation of the transmission-line matrix (TLM) method used to solve Maxwell's equations is the long computation time required. The TLM scattering calculations involved can, however, be viewed as parallel...
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A major limitation of the transmission-line matrix (TLM) method used to solve Maxwell's equations is the long computation time required. The TLM scattering calculations involved can, however, be viewed as parallel in nature. This paper describes an effort to reduce computational time by using an SIMD, DAP multiprocessor computer employed to solve a two-dimensional TLM electromagnetic field formulation. A parallel algorithm based on the TLM scattering algorithm is designed and implemented using FORTRAN-PLUS Enhanced on an AMT DAP 510 machine. Here the connectivity of the DAP is exploited to simulate the intrinsic scattering behaviour on which the TLM algorithm relies. The results show that parallel processing on an SIMD machine such as the DAP is advantageous, especially for higher-order mesh sizes.
A multi-language-based data interface system for heterogeneous distributed processing is introduced. A prototyped environment based on this system is discussed, and an evaluation of the prototyped system is presented....
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A multi-language-based data interface system for heterogeneous distributed processing is introduced. A prototyped environment based on this system is discussed, and an evaluation of the prototyped system is presented. It is shown that by keeping the syntax of the specification language flexible and close to existing high-level languages, a user can learn the interface language quickly. Semantically, this data interface views structured data as consisting of two parts: the data values themselves and the representation of the structure among the data values. Through this separation, it is possible to have pipelined data type checking and data conversion operations.< >
Two-Level Grammar (TLG) is proposed for the formal specification and automatic generation of software systems. TLG specifications are unique in that they are a structured form of natural language which is executable. ...
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作者：
KING, JFBARTON, DEJ. Fred King:is the manager of the Advanced Technology Department for Unisys in Reston
Virginia. He earned his Ph.D. in mathematics from the University of Houston in 1977. He has been principal investigator of research projects in knowledge engineering pattern recognition and heuristic problem-solving. Efforts include the development of a multi-temporal multispectral classifier for identifying graincrops using LANDSAT satellite imagery data for NASA. Also as a member of the research team for a NCI study with Baylor College of Medicine and NASA he helped develop techniques for detection of carcinoma using multispectral microphotometer scans of lung tissue. He established and became technical director of the AI Laboratory for Ford Aerospace where he developed expert scheduling modeling and knowledge acquisition systems for NASA. Since joining Unisys in 1985 he has led the development of object-oriented programming environments blackboard architectures data fusion techniques using neural networks and intelligent data base systems. Douglas E. Barton:is manager of Logistics Information Systems for Unisys in Reston
Virginia. He earned his B.A. degree in computer science from the College of William and Mary in 1978 and did postgraduate work in London as a Drapers Company scholar. Since joining Unisys in 1981 his work has concentrated on program management and software engineering of large scale data base management systems and design and implementation of knowledge-based systems in planning and logistics. As chairman of the Logistics Data Subcommittee of the National Security Industrial Association (NSIA) he led an industry initiative which examined concepts in knowledge-based systems in military logistics. His responsibilities also include evaluation development and tailoring of software engineering standards and procedures for data base and knowledge-based systems. He is currently program manager of the Navigation Information Management System which provides support to the Fleet Ballistic Missile Progr
A valuable technique during concept development is rapid prototyping of software for key design components. This approach is particularly useful when the optimum design approach is not readily apparent or several know...
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A valuable technique during concept development is rapid prototyping of software for key design components. This approach is particularly useful when the optimum design approach is not readily apparent or several known alternatives need to be rapidly evaluated. A problem inherent in rapid prototyping is the lack of a "target system" with which to interface. Some alternatives are to develop test driver libraries, integrate the prototype with an existing working simulator, or build one for the specific problem. This paper presents a unique approach to concept development using rapid prototyping for concept development and scenario-based simulation for concept verification. The rapid prototyping environment, derived from artificial intelligence technology, is based on a blackboard architecture. The rapid prototype simulation capability is provided through an object-oriented modeling environment. It is shown how both simulation and blackboard technologies are used collectively to rapidly gain insight into a tenacious problem. A specific example will be discussed where this approach was used to evolve the logic of a mission controller for an autonomous underwater vehicle.
Robot applications, represented as plans, are used to outline a viewpoint that robustness needs to be emphasized in two areas: in the plan representation and in the underlying system software. Robot applications are i...
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ISBN:
(纸本)0818620811
Robot applications, represented as plans, are used to outline a viewpoint that robustness needs to be emphasized in two areas: in the plan representation and in the underlying system software. Robot applications are inherently distributed, since the hardware usually comprises a set of independent actuators and sensors, with the robot programs acting as links between them. A special model of distributed computation, the RS (Robot Schemas) model, has been designed to handle the issues of robot plan representation, and an overview of the model is presented. An initial implementation of the model with minimal execution support demonstrated that the domain-dependent aspect of robustness on its own was not sufficient for robust behavior. Consequently, the OS has been augmented with real-time scheduling, and monitoring facilities.< >
The construction of real-time software for autonomous robot systems that can operate in an uncertain and dynamic environment is considered. Techniques for representing robust robot plans using the RS (robot schema) mo...
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The construction of real-time software for autonomous robot systems that can operate in an uncertain and dynamic environment is considered. Techniques for representing robust robot plans using the RS (robot schema) model are developed which make it possible to separate planned decision-making from error monitoring; they give a modular way to embed error detection, diagnosis, and recovery into plans, and via the formal tools of RS they allow one to analyze plans for error behavior. However, experience in implementing the RS kernel leads to the conclusion that robustness in the plan representation alone is not sufficient. Robustness must also be incorporated in the underlying system software to complement robustness in the plan representation model. Experiences with the initial implementation of the RS execution environment kernel also emphasized the need for operating system constructs that would support the robustness inherent in the model.< >
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