A two-step structure is proposed for the decision-making process that is needed when multiple versions of software are utilized to combat the effects of design errors. In addition to providing a simple framework for i...
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ISBN:
(纸本)0818606908
A two-step structure is proposed for the decision-making process that is needed when multiple versions of software are utilized to combat the effects of design errors. In addition to providing a simple framework for implementing a variety of adjudication strategies, the structure makes it possible to give a uniform description which encompasses the range of published solutions.
There is an increasing demand on using off-the-shelf (OTS) software components to facilitate the development of softwaresystems.distributedsoftwaresystems.are often too complex to develop from scratch. Therefore, ...
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ISBN:
(纸本)0769502911
There is an increasing demand on using off-the-shelf (OTS) software components to facilitate the development of softwaresystems.distributedsoftwaresystems.are often too complex to develop from scratch. Therefore, distributed system designers are motivated to deploy trusted software components resulting in a component-based nature of the system. Using OTS components could indicate a more reliable software. However, the sensitivity of the system reliability to component reliabilities needs further investigation based on reliability analysis models and techniques that are suitable for distributed component-based software. The distributed nature of these systems.further coerces the analysis technique to incorporate link and delivery channel reliabilities. This paper proposes a reliability analysis technique for distributedsoftwaresystems. The technique is based on scenarios that are modeled as sequence diagrams. Using scenarios, we construct Component-Dependency Graphs (CDG). CDGs have been introduced for reliability analysis of component-based systems. They are extended here to serve the complex nature of distributedsystems.by applying nesting and hierarchy. CDGs include component and link reliabilities, which are treated as first class elements of the model. Based on CDGs, we present an algorithm to analyze the sensitivity of system reliability to reliabilities of its components, subsystems. and links. The proposed analysis technique is useful in identifying critical components and critical component links. An example based on medical informatics standard is presented to illustrate our methodology.
In this paper we describe an infrastructure that provides increased reliability for three-tier applications, transparently, using commercial off-the-shelf application servers and databasesystems. In this infrastructu...
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In this paper we describe an infrastructure that provides increased reliability for three-tier applications, transparently, using commercial off-the-shelf application servers and databasesystems. In this infrastructure the application servers are actively replicated to protect the business logic processing. Replicating the transaction coordinator renders the two-phase commit protocol non-blocking and thus, avoids potentially long service disruptions caused by coordinator failure. A thin interpositioning library provides client-side automatic failover, so that clients know the outcome of their requests. The interaction between the application servers and the database servers is handled through replicated gateways that prevent duplicate requests from reaching the database servers. Aborted transactions, caused by process or communication faults, are automatically retried on the client's behalf.
NTT software Labs is producing a distributed, self-configuring information navigation infrastructure designed to scale to global proportions. For reasons of large scale, unreliability (of the Internet, its connected c...
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NTT software Labs is producing a distributed, self-configuring information navigation infrastructure designed to scale to global proportions. For reasons of large scale, unreliability (of the Internet, its connected computers, and the implementations), and the complete autonomy of the participants, a number of difficult database and cache consistency problems arise that are not solved by techniques commonly used either for the Internet (i.e. DNS), or for existing distributeddatabasesystems. This paper describes a set of strategies designed to solve these problems. In particular, it focuses on the use of third-party detection and notification of database and cache inconsistency.
This paper presents four models to demonstrate our techniques for optimizing software and hardware reliability for fault-tolerant distributedsystems. The models help us find the optimal system structure while conside...
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ISBN:
(纸本)0780366158
This paper presents four models to demonstrate our techniques for optimizing software and hardware reliability for fault-tolerant distributedsystems. The models help us find the optimal system structure while considering basic information on reliability and cost of the available software and hardware components. Each model is suitable for a distinct set of conditions or situations. All four models maximize reliability while meeting cost constraints. The Simulated Annealing optimization algorithm is selected to demonstrate system reliability optimization techniques for distributedsystems.because of its flexibility in applying to various problem types with various constraints, as well as its efficiency in computation time. It provides satisfactory reliability results while meeting the constraints.
An approach is presented that will allow database applications to increase availability in the face of network partitions and other communications failures, by permitting a controlled amount of nonserializable databas...
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ISBN:
(纸本)0818606908
An approach is presented that will allow database applications to increase availability in the face of network partitions and other communications failures, by permitting a controlled amount of nonserializable database activity. The underlying replicated database substrate ensures mutual consistency, without serializability, by timestamping all updates issued by database interactions. Compensating actions, triggered by exception conditions in the database, attempt to correct problems arising from nonserializable execution or notify human agents to investigate and correct the problem. Probabilistic concurrency control uses a controlled amount of inter-site synchronization to reduce the likelihood of nonserializable execution and the burden of compensation, at the cost of slightly reduced availability. This approach, illustrated by means of examples, allows application designers to tailor the system to achieve any desired balance between availability and consistency.
The Byzantine Generals problem involves a system of N processes, t of which may be unreliable. The problem is for the reliable processes to agree on a binary value sent by a 'general' which may itself be one o...
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The Byzantine Generals problem involves a system of N processes, t of which may be unreliable. The problem is for the reliable processes to agree on a binary value sent by a 'general' which may itself be one of the N processes. If the general sends the same value to each process, then all reliable processes must agree on that value but in any case, they must agree on the same value. An explicit solution is given for a binary value among N equals 3t plus 1 processes, using 2t plus 4 rounds and O(t**3 log t) message bits, where t bounds the number of faulty processes. This solution is easily extended to the general case of N greater than equivalent to 3t plus 1 to give a solution using 2t plus 5 rounds and O(tN plus t**3 log t) message bits.
This conference proceedings contains 19 papers. The following topics are dealt with: recovery;replication;network architecture;reliable communication;performance analysis;evaluation and modeling;and simulation and tes...
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This conference proceedings contains 19 papers. The following topics are dealt with: recovery;replication;network architecture;reliable communication;performance analysis;evaluation and modeling;and simulation and testing.
Error control codes have been widely adopted to design dependable storage systems. thus number of data accesses becomes numerous. Data access efficiency as well as energy saving are important problems. This paper prop...
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ISBN:
(纸本)9781479955848
Error control codes have been widely adopted to design dependable storage systems. thus number of data accesses becomes numerous. Data access efficiency as well as energy saving are important problems. This paper proposes a method which uses variable information word length for improving data access efficiency in dependable storage systems.
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