In a recent software development effort, an ARINC Research Corporation development team translated 500 system transactions into 11000 lines of code in Ada-compilable program design language (PDL). The team established...
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In a recent software development effort, an ARINC Research Corporation development team translated 500 system transactions into 11000 lines of code in Ada-compilable program design language (PDL). The team established rigorous data collection and review processes to collect and classify defect data and identify reliability growth in the PDL being produced. Two classes of defects for the coding process were defined: minor defects and logic defects. Data were collected by transaction, by defect type, and by lines of PDL. The defect analysis indicated that the learning process, and thus reliability growth, were different for the two defect classes. In addition, a period of reduced work load and changes in coding standards affected the observed defect rates for each class differently. As a result of this analysis effort, a database was established to track the coding process and to provide a basis for estimating various parameters of future efforts (e.g., time and cost) as well as the impact of process changes.< >
Computer Integrated Manufacturing is based on computer communication. Data exchange is done by connecting workstations, manufacturing cells, machine tools, robots, etc. by networks. Many protocols and standards are de...
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Computer Integrated Manufacturing is based on computer communication. Data exchange is done by connecting workstations, manufacturing cells, machine tools, robots, etc. by networks. Many protocols and standards are defined to ensure safety and reliability of communication. Usually one problem arises in CIM: software costs explode, because CIM solutions almost are specialised programs for one distinct environment. A second problem in automation are the hardware requirements for CIM-software. software developers assume, that appropriate hardware is present. Many software packages are available only for workstations and mainframes, which are much more expensive than simple PCs. In most cases small or medium sized enterprises do not have the financial power to buy- large computers and sophisticated software packages. They do not really need all the options and processing speed of these solutions. What they need are flexible, small programs, which can be adapted and supplemented easily and fast without external help. This paper presents an unusual approach to organise communication in small CIM systems. Microsoft Windows 3x Dynamic Data Exchange (DDE) combined with NetBIOS handle all data exchange and sessions. Both systems.use the client/server architecture and work together properly. MS-Windows is in use world-wide. NetBIOS is available for most of the common networks today. Using a small MS-Windows application for DDE-routing full DDE-communication is possible. For external databases or external LANs with different protocols some gateway applications can be designed, which are used as database or communication servers. Users can easily program new applications by hand of the various, really simple programming tools for MS-Windows.
The authors report a study of the dependability of the various communication topologies that can be used to construct a Delta-4 system. Single and dual bus and ring configurations are possible (based on 802.4, 802.5, ...
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ISBN:
(纸本)0818622601
The authors report a study of the dependability of the various communication topologies that can be used to construct a Delta-4 system. Single and dual bus and ring configurations are possible (based on 802.4, 802.5, and FDDI standards);the authors give closed-form expressions for the reliability and availability of each topology when repair is taken into account. It is shown that the dimensioning parameter in the dependability of the communication system is the coverage of the self-checking mechanisms built into the network attachment controllers.
The symposium Materials contain 21 papers. The following topics are dealt with: checkpointing and logging algorithms;backward recovery schemes;replication and parallelism;dependability modeling and assessment;agreemen...
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ISBN:
(纸本)0818622601
The symposium Materials contain 21 papers. The following topics are dealt with: checkpointing and logging algorithms;backward recovery schemes;replication and parallelism;dependability modeling and assessment;agreement;and garbage collection.
The authors present a novel formal approach to proving the correctness of distributedsystems.of replicated processes that commuicate by message passing. The notion of correctness introduced is based on the consistenc...
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ISBN:
(纸本)0818622601
The authors present a novel formal approach to proving the correctness of distributedsystems.of replicated processes that commuicate by message passing. The notion of correctness introduced is based on the consistency of the replicated system with its nonreplicated counterpart. The formal framework of CSP (communicating sequential processes) allows the proof of partial correctness and deadlock-freedom properties of the systems.of replicated processes. The authors also discuss how a replicated process may be implemented by N-base copies, a majority of which are non-faulty, and point out the necessity of coordinating the copies and the requirements they should satsify.
The proposed coordinator log transaction execution protocol centralizes logging on a per-transaction basis and exploits piggybacking to provide the semantics of a distributed atomic commit without the associated costs...
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The proposed coordinator log transaction execution protocol centralizes logging on a per-transaction basis and exploits piggybacking to provide the semantics of a distributed atomic commit without the associated costs. This protocol eliminates two rounds of messages (one phase) from the presumed commit protocol and dramatically reduces the number of log forces needed for distributed atomic commit. The authors compare the coordinator log transaction execution protocol with existing protocols, describe when it is desirable, and discuss how it affects the write-ahead log protocol and the database crash recovery algorithm.
distributed synchronization for data sharing is discussed, and the design of a distributed lock manager for the Camelot transaction facility is presented. The lock manager is a component of a proposed implementation o...
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distributed synchronization for data sharing is discussed, and the design of a distributed lock manager for the Camelot transaction facility is presented. The lock manager is a component of a proposed implementation of data sharing in the Camelot environment. A number of experiments that demonstrate the correct operation of the lock manager are reported and its performance is described. The performance metrics indicate that distributed lock management should not reduce the feasibility of data sharing in this environment. The similarity between the caching and synchronization strategies appropriate for locks and data suggests that protocols developed for distributed locks will be applicable to data sharing.
A recursive algorithm for computing a lower bound on the all-terminal reliability of an n-dimensional hypercube is presented. The recursive step decomposes an n-dimensional hypercube into lower dimension hypercubes th...
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A recursive algorithm for computing a lower bound on the all-terminal reliability of an n-dimensional hypercube is presented. The recursive step decomposes an n-dimensional hypercube into lower dimension hypercubes that are linked together. As an illustration of the effectiveness and power of this method, a lower bound is computed on the all-terminal reliability of the 16-dimensional hypercube (Connection Machine architecture) whose links number 219. The notation and assumptions are defined, and background information on bounding the reliability polynomial is provided. Methods for tightening these bounds for the analysis of the hypercube architecture are discussed.
The following topics are dealt with: distributed operating systems.local area networks;network fault tolerance;hypercubes;distributeddatabases;real-time systems.replicated programs;computer architectures;and voting. ...
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The following topics are dealt with: distributed operating systems.local area networks;network fault tolerance;hypercubes;distributeddatabases;real-time systems.replicated programs;computer architectures;and voting. Abstracts of individual papers can be found under the relevant classification codes in this or other issues.
Replicated execution of distributed programs, which provides a means of masking hardware (processor) failures in a distributed system, is discussed. Application-level entities (processes, objects) are replicated to ex...
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Replicated execution of distributed programs, which provides a means of masking hardware (processor) failures in a distributed system, is discussed. Application-level entities (processes, objects) are replicated to execute on distinct processors. Such replica entities communicate by message passing. Nondeterminism within the replicas could cause messages to be processed in nonidentical order, producing a divergence of state. Possible sources of nondeterminism are identified, and a generic mechanism for ensuring that nonfaulty replicas process messages in identical order, thereby preventing state divergence among such replicate entities, is presented.
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