D. Theodoratos and T. Sellis. Data warehouse design. In VLDB, 1997.  Home/Search   Document Not in Database   Summary   Related Articles   Check

.... using views) has recently received significant attention because of its relevance to a wide variety of data management problems [20] query optimization [6, 21, 36] maintenance of physical data independence [35, 33, 27] data integration [22, 9, 18, 19] and data warehouse and web site design [16, 32]. Informally speaking, the problem is the following. Suppose we are given a query over a database schema, and a set of view definitions 4670 38 over the same schema. Is it possible to answer the query using only the answers to the views 37536 , and if so, how There are ....

D. Theodoratos and T. Sellis. Data warehouse design. In VLDB, 1997.

....in this context because the number of views (i.e. sources) tends to be much larger, and the sources need not contain the complete extensions of the views. In the area of data warehouse design we need to choose a set of views (and indexes on the views) to materialize in the warehouse [HRU96, TS97, YKL97, GHRU97, ACN00, CG00] Similarly, in web site design, the performance of a web site can be signi cantly improved by choosing a set of views to materialize [FLSY99] In both of these problems, a rst step in determining the utility of a choice of views is to ensure that the views are ....

....Section 9 concludes, and outlines some of the open problems in this area. We note that this survey is not concerned with the closely related problems of incremental maintenance of materialized views, which is surveyed in [GM99b] selection of which views to maintain in a data warehouse [HRU96, TS97, GHRU97, Gup97, YKL97, GM99c, CG00] or automated selection of indexes [CN98b, CN98a] 2 Motivation and Illustrative Examples Before beginning the detailed technical discussion, we motivate the problem of answering queries using views through some of its applications. In particular, this section ....

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Dimitri Theodoratos and Timos Sellis. Data warehouse design. In Proc. of the Int. Conf. on Very Large Data Bases (VLDB), Athens, Greece, 1997.

....raises several research challenges. Most importantly, there is a need for algorithms that decide which data (and over which sources) need to be materialized. The problem we face is an extension to the problem of selecting views (and indexes) to materialize in a database system or data warehouse [17, 2]. The further complications in our context are because (1) the data sources are autonomous and may contain overlapping data, 2) we may need to adjust the set of materialized views over time depending on the query load, and (3) we do not have good cost estimates for querying over remote data ....

D. Theodoratos and T. Sellis. Data warehouse design. In Proc. of VLDB, Athens, Greece, 1997.

....sources) tends to be much larger, and the sources need not contain the complete extensions of the views. The problem of answering queries using views arises in the area of data warehouse and web site design, where we need to choose a set of views to materialize in the data warehouse [HRU96, TS97, YKL97, GHRU97] or a set of views to precompute in order to improve the performance of a web site [FLSY99] As a first step in choosing an optimal design for the data warehouse we must ensure that the chosen views can be used to answer the queries we expect to receive over the data warehouse. ....

....9 concludes, and outlines some of the open problems in this area. We note that this survey is not concerned with the closely related problems of incremental maintenance of materialized views, which is surveyed in [GM99b] and selection of which views to maintain in a data warehouse [HRU96, TS97, GHRU97, YKL97] 2 Motivation and Illustrative Examples Before beginning the detailed technical discussion, this section motivates the problem of answering queries using views through some of the applications in which it arises. We use the following familiar university schema in our examples ....

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Dimitri Theodoratos and Timos Sellis. Data warehouse design. In Proc. of the Int. Conf. on Very Large Data Bases (VLDB), Athens, Greece, 1997.

.... imposing a speci c mapping technique is not at all desirable; particular applications are entitled to their particular mappings, just as the view selection problem in the relational database world has long been identi ed as depending on the data and application characteristics (see, e.g. [27]) A frequent scenario of XML usage leads to the same conclusion: DTDs or Schemas are established for a particular application domain, and from then on, actors in the eld begin exchanging their (relational) data mapped to the standardized format. It is highly unlikely that a single mapping might ....

Dimitri Theodoratos and Timos Sellis. Data warehouse design. In Proc. of the VLDB Conf., Athens, Greece, 1997.

....to consider the set of parameterized queries that are executed against the database as a particular workload, and to apply some of the existing techniques proposed in the literature to optimize a given workload. Such techniques have been considered in various contexts, such as view materialization [18, 8, 9, 3], index selection, function caching [12, 11, 5] multiple query optimization [17] and reusing query invariants [13, 16] However, none of the above techniques exploit a key aspect of our context, namely the structure of the web site. The structure of a web site imposes a topology over the possible ....

....computations. The problem we face is to decide which set of views to materialize in order to optimize the behavior of the site. This problem of choosing a set of materialized views and the appropriate set of indices for a given query workload has received signi cant attention in recent literature [10, 18, 8, 9, 3]. Example 3.1 : Let s assume we decide to materialize the following view with an index on the attribute SK: V1(CK,SK,PK,CN) Customer(CK,CN, LineItem(OK, PK, SK, Order(OK,CK, The view V1 can be used in answering both Q8 and Q22. We measured considerable speedup rates: ....

D. Theodoratos and T. Sellis. Data warehouse design. In VLDB, Athens, Greece, 1997.

.... using views) has recently received significant attention because of its relevance to a wide variety of data management problems [20] query optimization [6, 21, 36] maintenance of physical data independence [35, 33, 27] data integration [22, 9, 18, 19] and data warehouse and web site design [16, 32]. Informally speaking, the problem is the following. Suppose we are given a query Q over a database schema, and a set of view definitions V 1 , Vn over the same schema. Is it possible to answer the query Q using only the answers to the views V 1 , Vn , and if so, how There are ....

D. Theodoratos and T. Sellis. Data warehouse design. In VLDB, 1997.

....to consider the set of parameterized queries that are executed against the database as a particular workload, and to apply some of the existing techniques proposed in the literature to optimize a given workload. Such techniques have been considered in various contexts, such as view materialization [13, 23, 10, 12, 11, 6], index selection [7] function caching [16, 14] multiple query optimization [22] and reusing query invariants [17, 21] However, none of the above techniques exploit a key aspect of our context, namely the structure of the web site. The structure of a web site imposes a topology over the ....

....in the site share similar computations. The problem we face is to decide which set of views V to materialize in order to optimize the behavior of the site. This problem of choosing a set of materialized views for a given query workload has received significant attention in recent literature [13, 23, 10, 12, 11, 6]. It is important to note that in our context it becomes even more important to consider selecting views and indexes on them at the same time. 5 Since the queries in our site definition are always parameterized, there are obvious heuristics for choosing the appropriate indexes. In addition we ....

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Dimitri Theodoratos and Timos Sellis. Data warehouse design. In Proc. of the Int. Conf. on Very Large Data Bases (VLDB), Athens, Greece, 1997.

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D. Theodoratos and T. Sellis. Data warehouse design. In VLDB, 1997.

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Dimitri Theodoratos and Timos Sellis. Data warehouse design. In VLDB, 1997.

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Dimitri Theodoratos and Timos Sellis. Data warehouse design. In Proc. of the 23rd Int. Conf. on Very Large Data Bases (VLDB'97), pages 126-135, 1997.

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