Most work on database integration has considered only support for data retrieval, not support for updates, and often the use for a special semantically rich data model has been required. The authors present an approac...
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ISBN:
(纸本)0818608935
Most work on database integration has considered only support for data retrieval, not support for updates, and often the use for a special semantically rich data model has been required. The authors present an approach to database integration which supports updates and which uses only the standard relational data model. Many of the ideas used in this approach are applicable to database integration in the context of other data models as well.
A novel, high-perfrmance subsystem for information retrieval called JAS is introduced. JAS sustains Gbyte/s comparison rates due to its 'early-out' CMOS substring search processor. The complexity of each JAS u...
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ISBN:
(纸本)0818608935
A novel, high-perfrmance subsystem for information retrieval called JAS is introduced. JAS sustains Gbyte/s comparison rates due to its 'early-out' CMOS substring search processor. The complexity of each JAS unit is independent of the complexity of the query. This independence is achieved by utilizing a decoupled instruction set. The JAS architecture is described, and its performance is evaluated.
The authors examine the issue of robust transaction routing in distributed database systems. A class of dynamic routing strategies which are estimated response times to make routing decisions is studied in details. Si...
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ISBN:
(纸本)0818608935
The authors examine the issue of robust transaction routing in distributed database systems. A class of dynamic routing strategies which are estimated response times to make routing decisions is studied in details. Since response time estimation and decision making depend on the assumed transaction model and parameers, it is important to examine the robustness or sensitivity to the inaccuracy in the assumptions and parameter values. Through simulations, the authors find that the dynamic routing strategy based strictly on response time is too aggressive in sharing loads and makes too many nonpreferred system routings. It is robust with respect to change in the number of database calls per transaction, but is relatively sensitive to the distribution of database calls. Two refinements are proposed which improve system performance as well as robustness of routing decisions.
An examination is made of heuristic algorithms for processing distributed queries using generalized joins. As this optimization problem is NP-hard, a heuristic algorithm is used to form/formulate strategies to process...
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ISBN:
(纸本)0818608935
An examination is made of heuristic algorithms for processing distributed queries using generalized joins. As this optimization problem is NP-hard, a heuristic algorithm is used to form/formulate strategies to process queries. It has a special property in that its overhead can be controlled. The higher its overhead the better the strategies it produces. Modeling on a testbed of queries demonstrates that there is a tradeoff between the strategy's execution and formulation delays. The modeling results also support the notion that simple greedy heuristic algorithms are sufficient in that they are likely to lead to near-optimal strategies and that increasing the overhead in forming strategies is only marginally beneficial. Both the strategy formulation and execution delays are examined in relation to the number of operations specified by the strategy and the total size of partial results.
The binary hypercube, a popular model for fault-tolerant interconnection networks, has been studied. It has been shown that, for a local area network based on a binary hypercube, having 2r nodes where every data is re...
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ISBN:
(纸本)0818608935
The binary hypercube, a popular model for fault-tolerant interconnection networks, has been studied. It has been shown that, for a local area network based on a binary hypercube, having 2r nodes where every data is replicated r times, in the absence of faults, any query involving an arbitrary sequency of n joins, n &le r, can be performed by repeatedly executing joins in a distributed fashion using n node disjoint paths from n/2 distinct sites of database operations to n arbitrary sites containing a target relation each. This protocol also solves the problem of materialization of relations. In the presence of up to r-2 faults, the protocol still guarantees N node disjoint paths to arbitrary sites. The value of N is determined by the number of faulty nodes.
The authors report a case study of an experimental distributed database system that they implemented on top of SunIngres, in a network of Sun 3/50 workstations connected by an Ethernet. They present and analyze measur...
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ISBN:
(纸本)0818608935
The authors report a case study of an experimental distributed database system that they implemented on top of SunIngres, in a network of Sun 3/50 workstations connected by an Ethernet. They present and analyze measurements for three algorithms based on the following strategies: (1) a fragment-and-replicate strategy, FRS;(2) a local reduction strategy, LR;and (3) an integrated strategy, integrating (1) and (2). A description is given of the test environment and the distributed query processing algorithms to be evaluated. A model to estimate data transmission cost is described, and measurements used to estimate data transfer cost are presented. The experimental design to evaluate the distributed query processing algorithm is sketched. Experimental results and interpretations of test results are provided. Experimental results reveal that the choices made by the integrated algorithm in deciding which relation should remain fragmented and which local operations to be performed are valid. More precisely, the response times of queries processed by the algorithm are lower than those of the same queries processed using other strategies. These experimental results agree with an analytic cost model which was previously proposed.
The authors propose a nontraditional system architecture for backend database processing, i.e., a network of workstations. By moving data dynamically to otherwise idle workstations over a local area network, a high de...
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ISBN:
(纸本)0818608935
The authors propose a nontraditional system architecture for backend database processing, i.e., a network of workstations. By moving data dynamically to otherwise idle workstations over a local area network, a high degree of processing parallelism could be achieved through load sharing. Three load-sharing join algorithms are developed and implemented on a network of Sun workstations. The algorithms are designed on the basis of different assumptions, e.g., whether indices are available and whether the join result is required to be sorted. Based on the analytical results and empmrical performance data for each algorithm, the authors show that the load-sharing strategy in each case is an effective method to achieve processing speedups. However, the network bandwidth of 10 Mb/s becomes a bottleneck when more than a dozen or so workstations are deployed, which indicates that a higher bandwidth network is needed for further improvement in performance.
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