The replication scheme of a distributed database determines how many replicas of each object are created, and to which processors these replicas are allocated. This scheme critically affects the performance of a distr...
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The replication scheme of a distributed database determines how many replicas of each object are created, and to which processors these replicas are allocated. This scheme critically affects the performance of a distributed system, since reading an object locally is less costly than reading it from a remote processor. Therefore in a read-intensive network a widely distributed replication is mandated. On the other hand, an update of an object is usually written to all, or a majority of the replicas, and therefore in a write-intensive network a narrowly distributed replication is mandated. In other words, the optimal replication scheme depends on the read-write pattern for each object. The authors propose a practical algorithm, called dynamic-data-allocation (DDA), that changes the replication scheme of an object (i.e. the processors which store a replica of the object) dynamically as the read-write pattern of the object changes in the network. They assume that the changes in the read-write pattern are not known a priori.< >
One of the most important problem, which arised during the creation of distributed software configurations (DSCs) for parallel systems and distributed computer control systems (DCCS), is deadlocks between interacting ...
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One of the most important problem, which arised during the creation of distributed software configurations (DSCs) for parallel systems and distributed computer control systems (DCCS), is deadlocks between interacting processes. Deadlocks are the subject of research, because their influence on normal computersystems behaviour is obvious. In the DCCS oriented software development system ALADDIN/LAMP during DSC debugging and maintenance the problem of deadlocks elimination also was faced. Programming language OCCAM was designed for development of DSCs runing on the transputer networks. This paper deals with the problem of DCCS software components operation reliability increasing by means of deadlock analysis and elimination. As the most important OCCAM language features as the approach to ALADDIN/LAMP tools extention for deadlocks analysis in OCCAM-written DSCs are presented.
Poisson processes with failure intensity functions that are approximately constant are investigated. Maximum likelihood estimation procedures are used to estimate the failure intensity for a fixed level of approximati...
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Model selection based on a predictive performance measure is compared to model selection based on maximum likelihood. Both procedures exhibit unstable relative performance when predictive performance is measured over ...
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Design for dependability has long been an important issue for computersystems. While several dependability analysis tools have been produced, no effort has been made to automate the design for dependability. This pap...
ISBN:
(纸本)9780897913638
Design for dependability has long been an important issue for computersystems. While several dependability analysis tools have been produced, no effort has been made to automate the design for dependability. This paper describes ASSURE, an automated design for dependability advisor, which is part of the MICON system for rapid prototyping of small computersystems. A design for dependability methodology and a formal interface between synthesis and dependability analysis are presented. ASSURE's operation includes dependability analysis, evaluation of dependability enhancement techniques using predictive estimation, and selection of a technique. Different kinds of knowledge used in designing for dependability are identified, including an algorithmic approach for dependability analysis and a knowledge-based approach for suggesting dependability enhancement techniques. Examples of designs produced using ASSURE as a dependability advisor are provided and show an order of magnitude dependability improvement.
作者：
Raymond JacobyYoshihiro TohmaTOSHIBA Corporation
Systems & Software Engineering Laboratory Saiwat-ku Kawasaki-shi 210 Japan and Department of Computer Science Tokyo Institute of Technology Ookayama 2-12-1 Meguro-Ku Tokyo Department of Computer Science
Tokyo Institute of Technology Ookayama 2-12-1 Meguro-Ku Tokyo
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.
A case study of the application of a distributed control scheme to a power system control is presented. In addition, an investigation has been conducted into voltage control. Combined injection of VAr-compensating dev...
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A case study of the application of a distributed control scheme to a power system control is presented. In addition, an investigation has been conducted into voltage control. Combined injection of VAr-compensating devices controlled by distributed expert systems has been proposed as a measure to maintain voltage stability in a power system under heavy loading conditions. A simulation study has been carried out by using five workstations that represent a power system and four VAr-compensating devices. The results demonstrate the effectiveness of the proposed system for voltage recovery.< >
The application of Petri net reduction to Ada-tasking deadlock detection is investigated. Net reduction can ease reachability analysis by reducing the size of the net while preserving relevant properties. By combining...
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The application of Petri net reduction to Ada-tasking deadlock detection is investigated. Net reduction can ease reachability analysis by reducing the size of the net while preserving relevant properties. By combining Petri net theory and knowledge of Ada-tasking semantics some specific efficient reduction rules are derived for Petri net models of Ada-tasking. A method by which a useful description of a detected deadlock state can be easily obtained from the reduced net's information is suggested.< >
Describes ASSURE, an automated design-for-dependability advisor, which is a part of the MICON system for rapid prototyping of small computersystems. A design-for-dependability methodology and a formal interface betwe...
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Describes ASSURE, an automated design-for-dependability advisor, which is a part of the MICON system for rapid prototyping of small computersystems. A design-for-dependability methodology and a formal interface between synthesis and dependability analysis are presented. ASSURE's operation includes dependability analysis, evaluation of dependability enhancement techniques using predictive estimation, and selection of a technique. Different kinds of knowledge used in designing for dependability are identified, including an algorithmic approach for dependability analysis and a knowledge-based approach for suggesting dependability enhancement techniques. Examples of designs produced using ASSURE as a dependability advisor are provided and show an order of magnitude dependability improvement.< >
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