Qiang Zhu and Per- Ake Larson. Solving local cost estimation problem for global query optimization in multidatabase systems. Distributed and Parallel Databases, 6(4):373--421, 1998.  Home/Search Document Details and Download
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Challenges in designing a QoS aware Media Repository - Sion, Elmagarmid.. (2000) (Correct)
.... time o Maximum Tolerable Synchronization (lip synchronization) Delay: maximum allowable di erential delay between the timebases of streams that have to be synchronized (e.g. audio with video) o Overall Cost: usually includes many sub costs such as the transmission charges and copyright fees [10]. 2.2 The query language Integrating QoS within a querying system also implies query language level extensions in syntax as well as in semantics. One considered alternative is an extended version of SQL. An example of such an extension may be a new clause QUALITY that a user can add to each ....
Qiang Zhu and Per-Ake Larson. Solving local cost estimation problem for global query optimization in multidatabase systems. Distributed and Parallel Databases, 6(4):373-420, October 1998. 8
Cost Models DO Matter: Providing Cost Information for.. - Roth, Özcan, Haas (27 citations) (Correct)
....suitable. The wrapper writer was only required to tailor the workload of queries used to generate the AVG RESET COST and AVG ADVANCE COST collection statistics so that they more accurately represented the data source s capabilities. We used a simple workload of queries; techniques described in [ZL98] might do a better job of choosing the appropriate sample queries. 4.2 Data Sources with Interesting Capabilities QBIC [N 93] is an image server that manages collections of images. These images may be retrieved and ordered according to features such as average color, color histogram, shape, ....
....model, and provide the optimizer with accurate enough information to make the right plan choices in many cases. However, we do not claim that our implementation is sufficient for the general case. We believe many of the techniques applied in [DKS92] and the approaches of more recent work of [ZL98] could be adapted to work within the context of the relational wrapper, and present an interesting area of research to pursue. 5 Experiments and Results In this section, we describe the results of experiments that show that the information provided by wrappers through our Query Pushdown join ....
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Q. Zhu and P. Larson. Solving local cost estimation problem for global query optimization in multidatabase systems. Distributed and Parallel Databases, 6:1--51, 1998.
Cost Models DO Matter: Providing Cost Information for.. - Roth, Özcan, Haas (27 citations) (Correct)
....that task. This information allows the optimizer to compute the cost of a plan without modifying its cost formulas or building in knowledge of the execution strategies of the external sources. Other work in this area has either assumed a single (relational) execution model for data sources [DKS92, ZL98, Cor97] required substantial changes to the optimizer [NGT98, ACPS96] or ignored costing altogether [LRO96, PGH96] We also show that cost based optimization is necessary in a heterogeneous environment; heuristic approaches [ACPS96, EDNO97, LOG93, ONK 96, SBM95] that push as much work as ....
....suitable. The wrapper writer was only required to tailor the workload of queries used to generate the AVG RESET COST and AVG ADVANCE COST collection statistics so that they more accurately represented the data source s capabilities. We used a simple workload of queries; techniques described in [ZL98] might do a better job of choosing the appropriate sample queries. 5.2. Data Sources with Interesting Capabilities QBIC [N 93] is an image server that manages collections of images. These images may be retrieved and ordered according to features such as average color, color histogram, shape, ....
[Article contains additional citation context not shown here]
Q. Zhu and P. Larson. Solving local cost estimation problem for global query optimization in multidatabase systems. Distributed and Parallel Databases, 6:1--51, 1998.
Classifying Local Queries For Global Query Optimization In.. - Zhu Self-citation (Zhu Larson) (Correct)
....for every query issued to a local DBS, which is used to estimate costs for similar queries. Roth et al. 16 introduced a framework for costing in the Garlic federated system. Zhu et al. 25 proposed a qualitative approach to developing cost models for a dynamic multidatabase environment. In [21,22,23], we introduced another method, called the query sampling method, to solve the problem. The key idea is to group local queries on a local DBS into homogeneous classes, draw a sample of queries from each query class, perform sample queries on the underlying DBS, and then use the observed costs of ....
....sampling queries from a query class) Query sampling is our new idea for query optimization. Apparently, the rst step of the query sampling method, i.e. classifying local queries, is crucial for derivation of local cost formulas. A good query classi cation can yield good cost formulas. In [21,23], only a simple classi cation approach, i.e. top down one, was described due to the limitation of the paper length. In this paper, we will discuss the issues for query classi cation in more details. In addition to the top down approach, another bottom up approach is introduced. The bottom up ....
[Article contains additional citation context not shown here]
Qiang Zhu and P.- A. Larson, Solving local cost estimation problem for global query optimization in multidatabase systems, Distributed and Parallel Databases, 6 (1998) 373-420.
Developing Cost Models with Qualitative Variables for.. - Zhu, Sun, Motheramgari (2000) (3 citations) Self-citation (Zhu) (Correct)
....a special local synthetic calibrating database and use the costs of some special queries run on the database to deduce the parameters in cost models. In [5] Gardarin et al. extended the above method so as to calibrate cost models for object oriented local database systems in an MDBS. In [17, 18, 19], Zhu and Larson proposed a query sampling method. The key idea is as follows. It first groups local queries that can be performed on a local DBS in an MDBS into homogeneous classes, based on some information available at the global level in an MDBS such as the characteristics of queries, operand ....
....clustering with merging adjustment (ICMA) respectively, are introduced. The former is used for general cases, while the latter is specifically designed for a dynamic environment with the contention level following a non uniform distribution with clusters. Our previous query sampling method in [17, 18, 19] is extended so as to develop a regression cost model incorporating the qualitative variable for a dynamic environment. Our approach in this paper is therefore an extension of our previous query sampling method. In this paper, we call our previous method as the static query sampling method and the ....
[Article contains additional citation context not shown here]
Q. Zhu and P.- A. Larson. Solving local cost estimation problem for global query optimization in multidatabase systems. Distributed and Parallel Databases, 6(4): 373 -- 420, 1998.
Query Brokers for Distributed and Flexible Query Evaluation - Vu, Collet (2003) (Correct)
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Qiang Zhu and Per- Ake Larson. Solving local cost estimation problem for global query optimization in multidatabase systems. Distributed and Parallel Databases, 6(4):373--421, 1998.
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