A. Tomasic, L. Raschid and P. Valduriez, A data model and query processing techniques for scaling access to distributed heterogeneous databases in disco, Invited paper in the IEEE Transaction Computers, Special Issue on Distributed Computing System 1997.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....no materialization and existing schemes such as page level caching. 1 Introduction There are several projects focusing on building information mediators, the representative systems include TSIM MIS [12] Information Manifold [13] The Internet Softbot [8] InfoSleuth [4] Infomaster [9] DISCO [19], HER MES [1] SIMS [3] and Ariadne [15] Many of these The research reported here was supported in part by the Integrated Media Systems Center, an NSF Engineering Research Center, in part by the United States Air Force under contract number F49620 98 1 0046, in part by the Jet Propulsion ....

A. Tomasic, L. Raschid, and P. Valduriez. A data model and query processing techniques for scaling access to distributed heterogeneous databases in disco. In Invited paper in the IEEE Transactionson Computers, special issue on Distributed Computing Systems, 1997.

....among information integration systems is the types of approaches used for query optimization. Systems addressing authorized integration of known databases can count on the availability of statistics on the databases (sources) being integrated. Thus Garlic [22] TSIMMIS [8] HERMES [3] and DISCO [41] systems attempt to use cost based optimization algorithms for query planning. Systems addressing information gathering scenarios, on the other hand, cannot count on having access to statistics about the information sources. Thus, either the mediator has to learn the statistics it needs, or will ....

Anthony Tomasic, Louiqua Raschid, and Patrick Valduriez. A data model and query processing techniques for scaling access to distributed heterogeneous databases in Disco. IEEE Transactions on Computers, special issue on Distributed Computing Systems, 1997.

....uses Garlic and wrapper rules to optimize a query across very different sources. Section 6 discusses related work, and Section 7 concludes the paper. 2 The Garlic System Figure 1 shows the architecture of Garlic [C 95] The architecture is typical of many heterogeneous database systems, e.g. [Day83, PGMW95, TRV96]. At the bottom are data sources, which store, access and manipulate data. Above every data source is a wrapper. A wrapper hides the details of the data source s interface and enables access to the data source using Garlic s internal protocols. The wrapper describes the data stored in the source ....

....query involving foreign tables and functions. Each version can then be optimized, and the least cost plan overall is chosen, Most work on cost based query optimization in heterogeneous systems is limited to specific classes of data sources [DKS92, GST96] The works most closely related to ours are [TRV96] (DISCO) and [PGH96] These two approaches also use grammars to describe the capabilities of wrappers; however, the types of grammars used and how they are used are significantly different. DISCO addresses problems beyond the scope of Garlic, with an emphasis on operating when not all data ....

A. Tomasic, L. Raschid, and P. Valduriez. A data model and query processing techniques for scaling acccess to distributed heterogeneous databases in DISCO, 1996. Submitted for publication.

....in optimizing mediator performance by materializing such classes. 1. Introduction There are several projects focusing on building information mediators, the representative systems include tsimmis [15] Information Manifold [16] The Internet Softbot [11] InfoSleuth [7] Infomaster [12] disco [24], hermes [2] sims [5] and Ariadne [18] Many of these systems allow database like querying of semi structured The research reported here was supported in part by the Integrated Media Systems Center, an NSF Engineering Research Center, in part by the United States Air Force under contract number ....

A. Tomasic, L. Raschid, and P. Valduriez. A data model and query processing techniques for scaling access to distributed heterogeneous databases in disco. In Invited paper in the IEEE Transactions on Computers, special issue on Distributed Computing Systems, 1997.

....which have small databases. STRUDEL s architecture, however, can accommodate either approach. Recent research addresses the problem of specifying the relationship between the mediated view of the data and the external data sources. Global as view (GAV) ADA 96, CHA 94, FLO 96, HAA 97, TOM 97] and Local as view (LAV) DUS 97a, DUS 97b, KWO 96, LEV 96a] are two techniques. In GAV, the relationship between the two relations is specified by a set of queries. For each relation R in the mediated schema, a query over the source relations specifies how to obtain R s tuples from the sources. ....

Tomasic A., Raschid L., Valduriez P., "A Data Model and Query Processing Techniques for Scaling Access to Distributed Heterogeneous Databases in Disco". IEEE Transactions on Computers, special issue on Distributed Computing Systems, 1997.

....data integration systems (e.g. 1 Work performed while the author was working in the AI Principles Research Department at AT T Laboratories. Preprint submitted to Elsevier Preprint 6 January TSIMMIS [8,18] HERMES [2] the Internet Softbot [15] SIMS [4] the Information Manifold [23] DISCO [16,29], Occam [20] Razor [17] Infomaster [11] is to provide a uniform query interface to the multiple data sources, thereby freeing the user from having to locate the relevant sources, query each one in isolation, and combine manually the information from the different sources. Data integration ....

A. Tomasic, L. Raschid, and P. Valduriez. A data model and query processing techniques for scaling access to distributed heterogeneous databases in Disco. IEEE Transactions on Computers, special issue on Distributed Computing Systems, 1997.

....query statement (done at mediator level) The semantic attachment operations and the consumers query profiles are the main techniques that are used for resolving semantics heterogeneity implied in the query results [LP97] 4. 4 DISCO DISCO, the Distributed Information Search COmponent [TRV96, TRV97] adopts the general mediator based paradigm, and can be seen as another concrete instance of the mediator based approach. The DISCO mediator data model is based on ODMG 93 data model specification. It extends the ODMG93 Object Definition Language (ODL) with two constructs: 1. Extents. An ....

A. Tomasic, L. Raschid, and P. Valduriez. A Data Model and Query Processing Techniques for Scaling Access to Distributed Heterogeneous Databases in Disco. IEEE Transactions on Computers, special issue on Distributed Computing Systems, 1997.

....and sufficed for our applications, which have small databases. Strudel s architecture, however, can accommodate either approach. Recent research addresses the problem of specifying the relationship between the mediated view of the data and the external data sources. Global as view (GAV) [2, 9, 17, 19, 23] and Local as view (LAV) 11, 18, 21] are two techniques. In GAV, the relationship between the two relations is specified by a set of queries. For each relation R in the mediated schema, a query over the source relations specifies how to obtain R s tuples from the sources. The LAV approach is the ....

A. Tomasic, L. Raschid, and P. Valduriez. A data model and query processing techniques for scaling access to distributed heterogeneous databases in Disco. IEEE Transactions on Computers, special issue on Distributed Computing Systems, 1997.

....domain of bibliographic sources available on the WWW. 1 Introduction The rise in the number of data sources available on line has led to the development of several mediator systems, also known as information integration systems) such as tsimmis [CGMH 94] hermes [ACPS96] disco [FRV96, TRV97] sims [AKS96] Permission to copy without fee all or part of this material is granted provided that the copies are not made or distributed for direct commercial advantage, the VLDB copyright notice and the title of the publication and its date appear, and notice is given that copying is by ....

A. Tomasic, L. Raschid, and P. Valduriez. A data model and query processing techniques for scaling access to distributed heterogeneous databases in disco. IEEE Transactions on Computers, special issue on Distributed Computing Systems, 1997.

....a research grant from General Dynamics Information Systems. The views and conclusions contained in this paper are the authors and should not be interpreted as representing the official opinion or policy of any of the above organizations or any person connected with them. O. Duschka 1997) disco (Tomasic, Raschid, Valduriez 1997), sims (Arens, Knoblock, Shen 1996) and Ariadne (Ambite et al. 1998) a descendant of sims focusing on integrating Web sources. Such systems allow database like querying of semi structured Web sources through wrappers around the Web sources, and also provide integrated access to multiple data ....

Tomasic, A.; Raschid, L.; and Valduriez, P. 1997. A data model and query processing techniques for scaling access to distributed heterogeneous databases in disco.

....domain of bibliographic sources available on the WWW. 1 Introduction The rise in the number of data sources available on line has led to the development of several mediator systems, also known as information integration systems) such as tsimmis [CGMH 94] hermes [ACPS96] disco [FRV96, TRV97] sims [AKS96] Permission to copy without fee all or part of this material is granted provided that the copies are not made or distributed for direct commercial advantage, the VLDB copyright notice and the title of the publication and its date appear, and notice is given that copying is by ....

A. Tomasic, L. Raschid, and P. Valduriez. A data model and query processing techniques for scaling access to distributed heterogeneous databases in disco. IEEE Transactions on Computers, special issue on Distributed Computing Systems, 1997.

.... on costbased query optimization is limited to specific classes of data sources; mostly, relational or object oriented databases [DKS92, GST96] Only recently have papers appeared that describe approaches to optimizing queries in systems with varying processing capabilities, e.g. PGH96, LRO96, TRV96a] We will discuss this related work in detail in Section 7. We believe ours is the first solution based on traditional dynamicprogramming techniques, with all the benefits we describe above. The remainder of this paper is structured as follows: Section 2 describes the Garlic architecture. Section ....

....from heterogeneous data sources, there is to date only limited work on query optimization in such an environment. Only recently have approaches to optimizing and decomposing queries considering diverse wrapper capabilities been proposed. The works most closely related to ours are DISCO [TRV96a] and Papakonstantinou et al. [PGH96] These two approaches also use grammars to describe the capabilities of wrappers; however, they differ significantly in the types of grammars used, and the way they are used during query optimization. DISCO addresses problems beyond the scope of Garlic, with an ....

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A. Tomasic, L. Raschid, and P. Valduriez. A data model and query processing techniques for scaling acccess to distributed heterogeneous databases in DISCO, 1996. Submitted for publication.

....be exploited when they are accessed through the middleware. Thus this first generation of middleware is not extensible to the arbitrary systems which may exist in a given business. Several projects are addressing the problem of middleware for increasingly diverse systems [Day83, S 94, PGMW95, TRV96, LRO96] Many of the data sources these systems integrate have limited or specialized query processing capabilities. Queries in this environment vary widely in performance depending on how and where their operations are executed. One key challenge for these systems is thus to develop a ....

....rules to optimize a query across very different sources. Section 6 discusses related work, and Section 7 concludes the paper. 2 The Garlic System Figure 1 shows the architecture of Garlic [C 95] The architecture is typical of many heterogeneous database systems, e.g. Day83, PGMW95, TRV96] At the bottom are data sources, which store, access and manipulate data. Above every data source is a wrapper. A wrapper hides the details of the data source s interface and enables access to the data source using Garlic s internal protocols. The wrapper describes the data stored in the source ....

[Article contains additional citation context not shown here]

A. Tomasic, L. Raschid, and P. Valduriez. A data model and query processing techniques for scaling acccess to distributed heterogeneous databases in DISCO, 1996. Submitted for publication.

....view, but rather on demand in each query. More recently work on languages to query structured and semi structured sources also provides higher order capabilities [32] Other proposals provide data model extensions to permit type extents (meta extents) to range over unspecified collections [36]. New extents can be added dynamically without changing the schema (type) specification. Meta extents are similar in motivation to the dynamic views we propose. However, dynamic views are more amenable to use in applications beyond integration, including those discussed in the introduction. ....

A. Tomasic, L. Raschid, and P. Valduriez. A Data Model and Query Processing Techniques for Scaling Access to Distributed Heterogeneous Databases in Disco. IEEE Trans on Computers, 1997.

....for our applications; Strudel s architecture, however, does not preclude a virtual approach. Recent research addresses the problem of specifying the relationship between the mediated view of the data and the external data sources. Two general approaches are advocated: Global as view (GAV) [6, 2, 12, 10, 16] and Local as view (LAV) 15, 14, 7, 8] Strudel currently uses the GAV approach. We justify our choice in Section 4. Query processor: Strudel provides a novel language, StruQL, for querying and restructuring semistructured data. Since data graphs and site graphs are represented in the same data ....

....the mediated schema into a query on the data sources, that have their own local schemas. Recent research addresses the problem of specifying the relationship between the relations in the mediated schema and those in the external sources. Two general approaches are advocated: Global as view (GAV) [6, 2, 12, 10, 16] and Local as view (LAV) 15, 14, 7, 8] These approaches are discussed for relational mediated schemas and source schemas. In the GAV approach, the relationship between the two types of relations is specified by a set of queries. For each relation R in the mediated schema, we write a query over ....

A. Tomasic, L. Raschid, and P. Valduriez. A data model and query processing techniques for scaling access to distributed heterogeneous databases in disco. IEEE Transactions on Computers, special issue on Distributed Computing Systems, 1997.

....The semantic attachment operations and the consumers 16 Ling Liu, Ling Ling Yan, M. Tamer Ozsu query profiles are the main techniques that are used for resolving semantic heterogeneity implied in the query results [LP97] 4. 4 DISCO DISCO, the Distributed Information Search COmponent [TRV96, TRV97] adopts the general mediator based paradigm, and can be seen as another concrete instance of the mediator based approach. The DISCO mediator data model is based on ODMG 93 data model specification. It extends the ODMG93 Object Definition Language (ODL) with two constructs: 1. Extents. An ....

A. Tomasic, L. Raschid, and P. Valduriez. A Data Model and Query Processing Techniques for Scaling Access to Distributed Heterogeneous Databases in Disco. IEEE Transactions on Computers, special issue on Distributed Computing Systems, 1997.

....cost based and enumerates the entire space of feasible plans, it finds good plans even in the presence of nonstandard data, strange methods, and unusual query processing capabilities. Only recently have other projects addressed the problem of optimization in this environment [FRV95, Qia96, PGH96, TRV97] Most take the approach of decomposing, or rewriting, the query into wrapperspecific pieces, and heuristically pushing down maximal pieces to the wrapper, though of course the actual means of decomposition varies. An exception is the optimizer of DISCO, which also does a cost based optimization ....

....Most take the approach of decomposing, or rewriting, the query into wrapperspecific pieces, and heuristically pushing down maximal pieces to the wrapper, though of course the actual means of decomposition varies. An exception is the optimizer of DISCO, which also does a cost based optimization [TRV97] However, DISCO enumerates plans as though all wrappers could handle any query, then uses wrapper grammars to filter out impossible plans. The Garlic optimizer, by contrast, enumerates only valid plans. We have chosen a Selinger style, dynamic programming approach to optimization because of its ....

A. Tomasic, L. Raschid, and P. Valduriez. A data model and query processing techniques for scaling acccess to distributed heterogeneous databases in DISCO. ACM Trans. Comp. Syst., 1997. To appear.

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A. Tomasic, L. Raschid and P. Valduriez, A data model and query processing techniques for scaling access to distributed heterogeneous databases in disco, Invited paper in the IEEE Transaction Computers, Special Issue on Distributed Computing System 1997.

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Anthony Tomasic, Louiqua Raschid, and Patrick Valduriez. A data model and query processing techniques for scaling access to distributed heterogeneous databases in Disco. IEEE Transactions on Computers, special issue on Distributed Computing Systems, 1997.

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A. Tomasic, L. Raschid, and P. Valduriez. A data model and query processing techniques for scaling access to distributed heterogeneous databases in Disco. IEEE Transactions on Computers, special issue on Distributed Computing Systems, 1997.

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A. Tomasic, L. Raschid and P. Valduriez, A data model and query processing techniques for scaling access to distributed heterogeneous databases in disco, Invited paper in the IEEE Transaction Computers, Special Issue on Distributed Computing System 1997.

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A. Tomasic, L. Raschid, P. Valduriez, A data model and query processing techniques for scaling access to distributed heterogeneous databases in disco, IEEE Trans. Comput. (Special issue on Distributed Computing Systems) (1997).

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Tomasic, A. et al . "A Data Model and Query Processing Techniques for Scaling Access to Distributed Heterogeneous Databases in Disco." In Review, 1996.

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