O. G. Tsatalos, M. H. Solomon, and Y. E. Ioannidis. The GMAP: A versatile tool for physical data independence. In Proc. VLDB, 1994.  Home/Search   Document Details and Download   Summary   Related Articles   Check

.... query on the sources would be q (title, subject) V(title, year, author) V2(title, subject) The LAV reformulation problem has received significant attention because of its relevance to other database problems, such as query optimization [7] maintaining physical data independence [22, 19], and data warehouse design. The GAV and the LAV strategies can be qualitatively or quantitatively [6] compared in terms of their adequacy (a) to model a particular integration situation, b) to cope with autonomy of the sources (sources changing their exported schemas, joining or leaving the ....

Tsatalos, O. G., Solomon, M. H., and Ioannidis, Y. E., 1994. The GMAP: A Versatile Tool for Physical Data Independence. Proceedings of the International Conference on Very Large Data Bases (VLDB), Santiago, Chile, pages 367-378.

....in star queries that are less complex than our experiments with EC2. Examples of SQO for OO systems appear in [8, 2, 10, 13, 7] A general framework for SQO using rewrite rules expressed using OQL appears in [12, 11] Techniques for using materialized views in query optimization are discussed in [5, 11, 12, 20, 3]. A survey of the area appears in [16] From our perspective, the work on join indexes [21] and precomputed access support relations [15] belongs here too. The general problem is forced by data independence: how to reformulate a query written against a user level schema into a plan that ....

....[21] and precomputed access support relations [15] belongs here too. The general problem is forced by data independence: how to reformulate a query written against a user level schema into a plan that also only uses physical access structures and materialized views eciently. The GMAP approach [20] works with a special case of conjunctive queries (PSJ queries) The core algorithm is exponential but the restriction to PSJ is used to provide polynomial algorithms for the steps of checking relevance of views and checking a restricted form of query equivalence. However, the results we report ....

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O. Tsatalos, M. Solomon, and Y. Ioannidis. The GMAP: A Versatile Tool for Physical Data Independence. VLDB Journal, 5(2):101-118, 1996.

.... by allowing more complicated physical storage schemas in addition to the base relations and indexes: relational materialized views [LMSS95, Lev, CKPS95] join indexes [Val87] access support relations for OO databases [KM90a, KM90b] sources with limited capabilities [RSU95, LRO96, FLMS99] GMAPs [TSI96] etc. In all these cases, the elements of the physical schema are defined as queries (views) over the logical schema. The advantage is that the logical schema is then fixed while the physical schema can be easily changed in order to achieve better storage, faster access, or simply in order to ....

....rewritings and applying the cost based optimization are combined, when possible, for efficiency reasons. Note that, in principle, the rewriting module takes over a part of the functionality of the traditional cost based module: finding the relevant indexes (when indexes are expressible as views [TSI96] Explore plans Logical query q Normalize Physical plan (operator tree) Logical query q Find rewritings that (views) join ordering) use physical schema Figure 1.2: Query optimizer architecture using materialized views. Another extension: semantic optimization. The ....

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O. Tsatalos, M. Solomon, and Y. Ioannidis. The GMAP: A Versatile Tool for Physical Data Independence. VLDB Journal, 5(2):101--118, 1996.

....above. The experimental configurations cover both relational and OO optimization, and the scenarios considered exhibit the systematic interaction between semantic and physical optimization that allows us to find high quality plans. Our experiments cover and go beyond the experiments of [CGK 99, TSI94, YL87, SO89] We reconstructed those experiments and found that our optimizer can also find the desired plans for a set of chosen queries. However, we went further by repeating the experiments on families of queries and schemas of similar structure but of increasing complexity. This allows us to ....

.... of referential integrity constraints to eliminate dependent joins is implicit in [JWKL90, CD92, KM90a, KM90b] A general framework for SQO using rewrite rules expressed 186 using OQL appears in [FRV96, Flo96] Techniques for using materialized views in query optimization are discussed in [YL87, TSI94, CKPS95, Flo96, FRV96, TSI96, Ba98] A survey of the area appears in [Lev] For us, the most important work here is probably that of [LMSS95] in which a finite search space for rewritings in the context of answering queries with materialized conjunctive views was found. There it was proved than ....

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Odysseas G. Tsatalos, Marvin H. Solomon, and Yannis E. Ioannidis. The GMAP: A Versatile Tool for Physical Data Independence. In Proc. of 20th VLDB Conference, pages 367--378, Santiago, Chile, 1994.

....still need techniques for a more radical decoupling of the logical schema from the physical implementation, while in information integration systems most difficulties come from heterogeneity. There have been several research efforts investigating physical data independence as the central issue [45, 20] or investigating closely related problems [48, 16, 27, 15, 30, 39, 38] All of them recognize physical data independence as an optimization problem: rewrite a query Q( written against a logical schema into an equivalent query plan Q ( Phi) written against a physical schema Phi, given a ....

.... an implementation mapping from to Phi, then solve X ffiI = Q for X then define Q = X (Here = means equality in the presence of the constraints of the logical schema ) The abstraction mapping approach is the one taken in [20] while the implementation mapping approach is the one taken in [45] and solving for X above is related to what is often called answering queries using views [30] The second approach is mathematically and computationally harder but it has a clear advantage from the optimization perspective: the equation X ffiI = Q typically has more than one solution, even ....

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O. Tsatalos, M. Solomon, and Y. Ioannidis. The gmap: A versatile tool for physical data independence. In Proc. of 20th VLDB Conference, Santiago, Chile, 1994.

....1 Introduction The problem of answering queries using views (a.k.a. rewriting queries 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 ....

....to answer the query using only the answers to the views 37536 , and if so, how There are two main contexts in which the problem of answering queries using views has been considered. In the first context, where the goal is query optimization or maintenance of physical data independence [35, 33, 6], we search for an expression that uses the views and is equivalent to the original query. Here it is usually assumed that the number of views is on the same order as the size of the schema. The second context is that of data integration, where views describe a set of autonomous heterogenous data ....

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O. G. Tsatalos, M. H. Solomon, and Y. E. Ioannidis. The GMAP: A versatile tool for physical data independence. VLDB Journal, 5(2):101--118, 1996.

....refer to row IDs. 1 This independence enables us to modify the storage schema of the data (i.e. the physical view) without changing its logical schema, and to model more complex types of indices. Hence, several authors describe the storage schema as a set of views over the logical schema [YL87, TSI96, Flo96] Given these descriptions of the storage, the problem of computing a query execution plan (which, of course, must access the physical storage) involves guring out how to use the views to answer the query. A second class of applications in which our problem arises is data integration. ....

....also to make a judicious cost based decision on when to use the available views. 2. 2 Maintaining Physical Data Independence Several of the works on answering queries using views were inspired by the goal of maintaining physical data independence in relational and object oriented databases [YL87, TSI96, Flo96] One of the principles underlying modern database systems is the separation between the logical view of 4 Evaluation Advises Quarter Quarter Faculty Department Course name area name c number worksIn teaches title major name registered Student Figure 1: An ....

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Odysseas G. Tsatalos, Marvin H. Solomon, and Yannis E. Ioannidis. The GMAP: A versatile tool for physical data independence. VLDB Journal, 5(2):101-118, 1996.

....with V1. Even though this plan may seem redundant compared to V1 1 V2, it may be cheaper depending on the available indexes on the views, because it enables pruning the (possibly larger) set of students based on the selective course number. Variations on the above principles are presented in [TSI94, TSI96] and [CKPS95] The algorithm in [TSI96] attempts to reformulate a query on a logical schema to refer directly to GMAPs storing the data (see Section 2) They consider select project join queries with set semantics. To test whether a solution is complete (i.e. whether it is equivalent to ....

Odysseas G. Tsatalos, Marvin H. Solomon, and Yannis E. Ioannidis. The GMAP: A versatile tool for physical data independence. In Proc. of the Int. Conf. on Very Large Data Bases (VLDB), pages 367-378, Santiago, Chile, 1994.

....of the physical view of the data and its logical view. This independence enables us to modify the storage schema of the data (i.e. the physical view) without changing its logical schema. Hence, several authors have proposed to describe the storage schema as a set of views over the logical schema [45, 43, 24, 19]. Given these descriptions of the storage, the problem of computing a query execution plan (which, of course, must access the physical storage) involves guring out how to use the views to answer the query. A second context in which our problem arises is data integration. A data integration ....

Odysseas G. Tsatalos, Marvin H. Solomon, and Yannis E. Ioannidis. The GMAP: A versatile tool for physical data independence. VLDB Journal, 5(2):101-118, 1996.

....view. This independence enables us to modify the storage schema of the data (i.e. the physical view) without changing its logical schema, and to model more complex types of indices. Hence, several authors proposed to describe the storage schema as a set of views over the logical schema [YL87, TSI96, Flo96] Given these descriptions of the storage, the problem of computing a query execution plan (which, of course, must access the physical storage) involves figuring out how to use the views to answer the query. A second class of applications in which our problem arises is data integration. ....

....title Figure 1: An Entity Relationship diagram for the university domain. 2. 2 Maintaining Physical Data Independence Several of the works on answering queries using views were inspired by the goal of maintaining physical data independence in relational and object oriented databases [YL87, TSI96, Flo96] One of the principles underlying modern database systems is the separation between the logical view of the data (e.g. as tables with their named attributes) and the physical view of the data (i.e. how it is layed out on disk) Relational database systems, even though they provide this ....

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Odysseas G. Tsatalos, Marvin H. Solomon, and Yannis E. Ioannidis. The GMAP: A versatile tool for physical data independence. VLDB Journal, 5(2):101--118, 1996.

....another, prune it. c) If the query has only 2 relations, stop. c) If there are no partial solutions, stop. Iteration 3 Iteration 3 . Figure 4: A comparison of a traditional query optimizer with one that exploits materialized views. Variations on the above algorithm are presented in [TSI94, TSI96] and [CKPS95] The algorithm in [TSI96] attempts to reformulate a query on a logical schema to refer directly to GMAPs storing the data (see Section 2) They consider select project join queries with set semantics. To test whether a solution is complete (i.e. whether it is equivalent to ....

Odysseas G. Tsatalos, Marvin H. Solomon, and Yannis E. Ioannidis. The GMAP: A versatile tool for physical data independence. In Proc. of the Int. Conf. on Very Large Data Bases (VLDB), pages 367--378, Santiago, Chile, 1994.

....look up the Price and Finance attribute from Dealer3 using the value of CarID for each tuple in the current answer set. This is likely to be much cheaper than computing a three way join from scratch. 2 1.2. Related Work Previous work on using views to answer queries includes [LY85, YL87, SJGP90, TSI94, CR94, CKPS95, LMSS95, RSU95] Subsequently, GHQ95, SDJY96] discuss how to answer aggregate queries using materialized aggregate views. TSI94, CKPS95] also describe how to incorporate their techniques in a traditional cost based query optimizer. The problem of view adaptation is related to the ....

....cheaper than computing a three way join from scratch. 2 1.2. Related Work Previous work on using views to answer queries includes [LY85, YL87, SJGP90, TSI94, CR94, CKPS95, LMSS95, RSU95] Subsequently, GHQ95, SDJY96] discuss how to answer aggregate queries using materialized aggregate views. TSI94, CKPS95] also describe how to incorporate their techniques in a traditional cost based query optimizer. The problem of view adaptation is related to the problem of query answering using views. However, a fundamental di#erence is that view adaptation doesn t have to compute the full answer set for ....

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Odysseas G. Tsatalos, Marvin H. Solomon, and Yannis E. Ioannidis. The GMAP: A versatile tool for physical data independence. In Bocca et al. VLDB, pages 367--378, 1994.

....independence This three levels approach has a big practical advantage: it separates the logical and physical views of the data, and decouples query translation from the identi cation of the tables needed to answer the XML queries. The logical physical independence, following the idea from GMaps [28], introduces more degrees of freedom in linking relational and XML data; for example, if a new table containing XML information is added, the whole mapping does not need to change: we only need provide a de nition of the table as a view over the generic schema. Forbidding access to a table is also ....

Odysseas G. Tsatalos, Marvin H. Solomon, and Yannis E. Ioannidis. The GMAP: A versatile tool for physical data independence. In Proc. of the VLDB Conf., pages 367378, Santiago, Chile, 1994.

....of built in predicates as discussed above and discuss necessary extensions to our algorithm for each case. We also show the utility and completeness of our algorithm for checking containment. Folding algorithms for conjunctive queries and views with built in predicates have been developed in [5, 19, 22]. The algorithms employed all use exhaustive search strategies that are exponential time in complexity, and do not guarantee to find all foldings. The algorithms in [19, 22] compute only foldings that depend solely on the views. When such complete foldings do not exist, partial foldings that are ....

....checking containment. Folding algorithms for conjunctive queries and views with built in predicates have been developed in [5, 19, 22] The algorithms employed all use exhaustive search strategies that are exponential time in complexity, and do not guarantee to find all foldings. The algorithms in [19, 22] compute only foldings that depend solely on the views. When such complete foldings do not exist, partial foldings that are contained in the original query or depend partially on the views could be very useful in practice, especially in the distributed environment. The other important difference ....

O. G. Tsatalos, M. H. Solomon, and Y. E. Ioannidis. The GMAP: A versatile tool for physical data independence. In Proceedings of the Twentieth International Conference on Very Large Data Bases, pages 367--378. Morgan Kaufmann, 1994.

....source schemas. In this case, reformulation amounts to unfolding the user s query. Local as view (LAV) 82, 72, 37, 38, 51, 73] the data sources are described as queries over the relations in the mediated schema. Here query reformulation reduces to the problem of answering queries using views [80, 36, 123, 117, 23, 108]. Description Logics: 22, 82] the mediated schema and the data sources are described as a terminology in some Description Logic. Query reformulation makes use of the subsumption and satis ability algorithms provided by the Description Logic system. Planning operators: 40, 54, 7, 72] data ....

Odysseas G. Tsatalos, Marvin H. Solomon, and Yannis E. Ioannidis. The GMAP: A versatile tool for physical data independence. VLDB Journal, 5(2):101-118, 1996.

....such as horizontal and vertical partitioning, materialized views, and hierarchical clustering, by means of a (nested relational) query algebra and also showed that an algebraic query rewrite optimizer can produce efficient execution plans. The GMAP tool is a recent attempt in the same direction [TSI94] they also provide a descriptive way to define physical schemas within a query language and provide query transformations and optimization. They have also started to look into update transformation, but in general did not consider heavily replicated physical designs. To describe the mapping of ....

Odysseas G. Tsatalos, Marvin H. Solomon, and Yannis E. Ioannidis. The GMAP: A Versatile Tool for Physical Data Independence. In Proceedings of the Twentieth International Conference on Very Large Databases, pages 367--378, Santiago, Chile, 1994.

....1 Introduction The problem of answering queries using views (a.k.a. rewriting queries 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 ....

....answer the query Q using only the answers to the views V 1 , Vn , and if so, how There are two main contexts in which the problem of answering queries using views has been considered. In the first context, where the goal is query optimization or maintenance of physical data independence [35, 33, 6], we search for an expression that uses the views and is equivalent to the original query. Here it is usually assumed that the number of views is on the same order as the size of the schema. The second context is that of data integration, where views describe a set of autonomous heterogenous data ....

[Article contains additional citation context not shown here]

O. G. Tsatalos, M. H. Solomon, and Y. E. Ioannidis. The GMAP: A versatile tool for physical data independence. VLDB Journal, 5(2):101--118, 1996.

....completing a mapping, and determining equivalence of models. For example, a mapping can be thought of as a view of one model in terms of another. Therefore, inverting a mapping resembles the problem of inverting views, which raises the relevance of work on answering queries using views [YL87, TSI96, CKPS95, LMSS95, DG97, FRV96] Even in the relational case these works need to be extended for the problems faced in model management, not to mention extensions to other contexts. Description Logics provide another formalism that has been shown to be useful for modeling DB schemas and interschema ....

Odysseas G. Tsatalos, Marvin H. Solomon, and Yannis E. Ioannidis. The GMAP: A versatile tool for physical data independence. VLDB Journal, 5(2):101--118, 1996.

....and Storage by Views. The generic relational schema is used to logically describe the content of data sources; in order to specify the actual storage and the access patterns supported by the sources, Agora allows for defining views with binding patterns (in a manner similar to that described in [11]. The view definitions can be arbitrarily complex, and by consulting them, the query processor is informed of the alternative ways to access the data, as well as the costs involved. As an example, let us consider the DOM method call retrieving all elements with a specific tag within a given ....

O. G. Tsatalos, M. H. Solomon, and Y. E. Ioannidis. The GMAP: A versatile tool for physical data independence. In Proc. of the Int. Conf. on Very Large Data Bases (VLDB), pages 367--378, Santiago, Chile, 1994.

....LMSS95] also tackle the problem of answering a query given any set of view definitions. They do not consider aggregate queries. Subsequently, DJLS95, GHQ95] discuss how to answer aggregate queries using materialized aggregate views. Their results subsume the results presented in Section 4. TSI94] focuses on the broader issue of enhancing physical data independence using gmaps. They use a logical schema and then specify the underlying physical storage structures as results of gmap queries on the logical schema. User queries on the logical schema are rewritten using one or more gmap ....

Odysseas G. Tsatalos, Marvin H. Solomon, and Yannis E. Ioannidis. The GMAP: A versatile tool for physical data independence. In Bocca et al. VLDB, pages 367--378, 1994.

....site. Client queries can be answered more efficiently if they can be folded using the cached data [9, 6] In the case of a disconnected network, a query can still be answered, at least partially, if it can be folded using views and queries maintained at available sites. A number of algorithms [3, 10, 15, 16, 18] have been developed for folding of conjunctive queries and resources. Some of these, including [3, 16, 18] were developed for purposes of optimization and, accordingly, seek to produce foldings (as in Example 1) that are equivalent to the original query. However, there are also applications for ....

....case of a disconnected network, a query can still be answered, at least partially, if it can be folded using views and queries maintained at available sites. A number of algorithms [3, 10, 15, 16, 18] have been developed for folding of conjunctive queries and resources. Some of these, including [3, 16, 18], were developed for purposes of optimization and, accordingly, seek to produce foldings (as in Example 1) that are equivalent to the original query. However, there are also applications for foldings that are known only to be contained in the original query. For example, a user may wish to ....

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O. G. Tsatalos, M. H. Solomon, and Y. E. Ioannidis. The GMAP: A versatile tool for physical data independence. In Proceedings of 20th VLDB, pages 367--378, 1994.

.... combination of query processing and view maintenance cost) is minimal The DW configuration problem is more complicated than other query or view maintenance optimization problems using views for the following reasons: ffl When views are kept materialized, in order to minimize the query evaluation [30, 4, 13, 12] or the view maintenance cost [20] queries possibly need to be answered using some materialized views. In the context of the DW configuration problem all the queries need to be answered using exclusively materialized views. In other words, there is the following additional constraint: for every ....

....is treated in Section 5. Section 6 contains concluding remarks and possible extensions. An extended version of this work appears on [29] 2 Related work The DW configuration problem relates to several overlapping research areas. Answering queries using materialized views has been studied in [14, 34, 30, 15, 4]. The same issue, in connection to aggregate queries and views, has been studied in [7] while in [5] multiset semantics is additionally considered. The problem of optimizing query evaluation in the presence of materialized views has been studied in [30, 4] The problem of maintaining ....

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O. G. Tsatalos, M. H. Solomon, and Y. E. Ioannidis. The GMAP: A versatile tool for physical data independence. In Proc. of VLDB, pages 367--378, 1994.

....Experiments We have built a prototype implementation of the C B technique for path conjunctive queries and constraints. With this implementation, we have used three experimental con gurations to answer the questions summarized above. In choosing them, we took as a starting point the experiments of [7, 31, 33, 29]. We reconstructed those experiments and found that our optimizer can also nd the desired plans for a set of chosen queries. However, we went further by repeating the experiments on families of queries and schemas of similar structure but of increasing complexity. This allows us to nd out how ....

.... 10, 9, 3, 14, 13, 17, 8] Use of referential integrity constraints to eliminate dependent joins is implicit in [19, 10, 20, 21] A general framework for SQO using rewrite rules expressed using OQL appears in [16, 15] Techniques for using materialized views in query optimization are discussed in [33, 31, 6, 15, 16, 30, 12]. A survey of the area appears in [22] From our perspective, the work on join indexes [32] and precomputed access support relations [20, 21] belongs here too. The general problem is forced by data independence: how to reformulate a query written against a user level schema into a plan that ....

[Article contains additional citation context not shown here]

Odysseas G. Tsatalos, Marvin H. Solomon, and Yannis E. Ioannidis. The GMAP: A Versatile Tool for Physical Data Independence. In Proc. of 20th VLDB Conference, pages 367-378, Santiago, Chile, 1994.

.... 10, 9, 3, 14, 13, 17, 8] Use of referential integrity constraints to eliminate dependent joins is implicit in [19, 10, 20, 21] A general framework for SQO using rewrite rules expressed using OQL appears in [16, 15] Techniques for using materialized views in query optimization are discussed in [33, 31, 6, 15, 16, 30, 12]. A survey of the area appears in [22] From our perspective, the work on join indexes [32] and precomputed access support relations [20, 21] belongs here too. The general problem is forced by data independence: how to reformulate a query written against a user level schema into a plan that ....

....and precomputed access support relations [20, 21] belongs here too. The general problem is forced by data independence: how to reformulate a query written against a user level schema into a plan that also only uses physical access structures and materialized views eciently. The GMAP approach [31, 30] works with a special case of conjunctive queries (PSJ queries) In contrast to the query plans obtained by our rewriting process, the output of the GMAP rewriting is a family of plans represented by a PSJ query. The burden of choosing a speci c plan is shifted on the next phase of the optimizer. ....

[Article contains additional citation context not shown here]

O. Tsatalos, M. Solomon, and Y. Ioannidis. The GMAP: A Versatile Tool for Physical Data Independence. VLDB Journal, 5(2):101-118, 1996.

....replicated, and locating as well as accessing them may be expensive. Locally cached materialized views of the data, such as the results of previous queries, may improve the performance of such applications. Data warehousing [GJM96, ZGMHW95] view adaptation [GMR95] and physical data independence [TSI94] involve the usage of materialized views (conceptual relations) to integrate data from multiple sources or to hide schema differences or physical storage details. The underlying relations may be expensive to access or may not be available, requiring queries against these relations to be processed ....

....conditions that utilize information about set valued queries and views, such as the existence of keys or SELECT DISTINCT. 1 In particular, we assume that there are no view tables in the FROM clause of the query or the view. 2 There has been previous work on using views to answer queries (e.g. [YL87, CKPS95, SJGP90, TSI94, CR94]) but the formal aspects of finding the equivalent rewritings for SQL queries with multiset semantics, grouping and aggregation, have received little attention. Most of the work has focused on conjunctive queries (i.e. without grouping and aggregation) with set semantics. One exception is the ....

[Article contains additional citation context not shown here]

Odysseas G. Tsatalos, Marvin H. Solomon, and Yannis E. Ioannidis. The GMAP: A versatile tool for physical data independence. In Proceedings of the International Conference on Very Large Databases, pages 367--378, Santiago, Chile, September 1994.

....by McGraw Hill . 3. Join the results of q1 and q2 to get the answer to the user query. Note that the feasibility of this plan is dependent on the source capabilities. Several works have considered the problem of implementing a query processor that uses the results of materialized views [56,43,46, 12, 55, 10]. 10,55,56]developed solutions to query folding or rewritings for conjunctive queries and resources with built in predicates. These solutions are based on either finding syntactic or 1 1 mappings from the view to the query. Their algorithms use exhaustive search strategies that are ....

....3. Join the results of q1 and q2 to get the answer to the user query. Note that the feasibility of this plan is dependent on the source capabilities. Several works have considered the problem of implementing a query processor that uses the results of materialized views [56,43,46, 12, 55, 10] [10,55,56]developed solutions to query folding or rewritings for conjunctive queries and resources with built in predicates. These solutions are based on either finding syntactic or 1 1 mappings from the view to the query. Their algorithms use exhaustive search strategies that are exponential time in ....

O.G. Tsatalos, M.H. Solomon, and Y.E. Ioannidis. The gmap: A versatile tool for physical data independence. In Proc. of Int. ConferenceonVery Large Databases, pages 367--378, 1994.

....problem of choosing a set of primary views such that the cost of (1) is minimized, while ensuring that the costs of (2) and (3) are not too high. SP89] considers this problem in the case of distributed views. HRU96] has investigated this problem for the case of aggregate views. Tsatalos et al. [TSI94] consider materializing views in place of the base relations in order to improve query response time. Rozen et al. RS91] look at this problem as adding a set of features to the database. In particular, the index selection part of our VIS problem has been well studied [FST88,CBC93] in the ....

O.G. Tsatalos, M.H. Solomon, and Y.E. Ioannidis. The gmap: A versatile tool for physical data independence. In Proceedings of International Conference on Very Large Data Bases, pages 367--78, 1994.

....to support such schema independent querying required in database publishing environments. Techniques for Physical Data Independence: An important technique used in indexing architectures for integrating new indexes into a query optimizer is the usage of views for describing the indexes [CKPS95, TSY96] Conventional techniques (such as [TSY96] are restricted in that they can only describe indexes that conform to the class of select project join views [Mil98] Miller [Mil98] gives examples of B tree indexes for all subclasses of a class, that can be expressed in SchemaSQL but not in SQL. ....

....required in database publishing environments. Techniques for Physical Data Independence: An important technique used in indexing architectures for integrating new indexes into a query optimizer is the usage of views for describing the indexes [CKPS95, TSY96] Conventional techniques (such as [TSY96] are restricted in that they can only describe indexes that conform to the class of select project join views [Mil98] Miller [Mil98] gives examples of B tree indexes for all subclasses of a class, that can be expressed in SchemaSQL but not in SQL. Besides, she also shows that the ....

O. Tsatalos et al. The GMAP: A Versatile Tool for Physical Data Independence. VLDB Jl, 5(2), April 1996.

....to the binding pattern limitations on the relations. Before we begin our discussion, we note several closely related problems that are not treated in this paper. As we noted earlier, binding patterns are a method for providing the query optimizer explicit descriptions of the data storage. GMAPs [5, 22] are also a method for describing storage structures. The focus of GMAPs is on describing groupings of the data in a data structure rather than describing limited access patterns to the data. In Section 8 we discuss how these two disjoint classes of storage descriptions can be combined. RR ....

....attempts to apply dioeerent search paradigms. As we stated in the introduction, one of the reasons for the existence of limited access patterns is the mismatch between the logical and physical views of the data. In our work, binding patterns were used to describe such mismatches. Tsatalos et al. [22] describe GMAPs which are also a mechanism for describing dioeerent storage patterns of the data. Using GMAPs, one can describe storage structures in which the stored data is a result of projections, selections and joins on the logical schema of the data. For example, using GMAPs it is possible to ....

[Article contains additional citation context not shown here]

Odysseas G. Tsatalos, Marvin H. Solomon and Yannis E. Ioannidis. The GMAP: A Versatile Tool for Physical Data Independence. In International Conference on Very Large Databases Journal, 5(2):101118, 1996.

....to the binding pattern limitations on the relations. Before we begin our discussion, we note several closely related problems that are not treated in this paper. As we noted earlier, binding patterns are a method for providing the query optimizer explicit descriptions of the data storage. GMAPs [5, 22] are also a method for describing storage structures. The focus of GMAPs is on describing groupings of the data in a data structure rather than describing limited access patterns to the data. In Section 8 we discuss how these two disjoint classes of storage descriptions can be combined. RR ....

Odysseas G. Tsatalos, Marvin H. Solomon and Yannis E. Ioannidis. The GMAP: A Versatile Tool for Physical Data Independence. In Proceedings of the 20th International Conference on Very Large Databases, Santiago, Chile, pages 367378, 1997.

.... review) The reformulated query on the sources would be: q 0 (title; review) GammaV 1 (title; year; director) V 2 (title; review) The LAV reformulation problem is very closely related to the problem of answering queries using views, studied in the database literature [YL87, TSI96, LMSS95, CKPS95, RSU95, DG97b] This problem has received significant attention because of its relevance to other database problems, such as query optimization [CKPS95] maintaining physical data independence [YL87, TSI96] and data warehouse design. As it turns out, the query reformulation ....

.... of answering queries using views, studied in the database literature [YL87, TSI96, LMSS95, CKPS95, RSU95, DG97b] This problem has received significant attention because of its relevance to other database problems, such as query optimization [CKPS95] maintaining physical data independence [YL87, TSI96] and data warehouse design. As it turns out, the query reformulation problem is in general NP complete in the size of the source descriptions and user query even when the queries describing the sources and the user query are conjunctive and don t contain interpreted predicates [LMSS95] However, ....

Odysseas G. Tsatalos, Marvin H. Solomon, and Yannis E. Ioannidis. The GMAP: A versatile tool for physical data independence. VLDB Journal, 5(2):101--118, 1996.

.... attention because of its applications in mediator systems (e.g. Information Manifold [LRO96] TSIMMIS [CGMH 94, PGGMU95] SIMS [AKS96] HERMES [ACPS96] Razor [FW97] Infomaster [DG97] Mobile Computing [BI94, HSW94] view adaptation [GMR95] maintaining physical data independence [TSI96] and speeding up query processing [YL87, CKPS95] The problem arises naturally in mediator systems that provide access to multiple heterogeneous information sources [Ull97] In such systems, The work was done while the first author was at AT T Laboratories. The work of the second and third ....

Odysseas G. Tsatalos, Marvin H. Solomon, and Yannis E. Ioannidis. The GMAP: A versatile tool for physical data independence. VLDB Journal, 5(2):101--118, 1996.

....plan is the same as the problem of rewriting queries using views. In this context, the views are the relations in the sources. The problem of rewriting queries using views has also been investigated in the database literature because of its importance for query optimization and data warehousing [32,30,6,22,26,25,10]. Most previous work has considered the problem of finding query plans where the query plan is required to be equivalent to the original query. In practice, the collection of available data sources may not contain all the information needed to answer a query, and therefore, we need to resort to ....

....by the ability of a source to answer a potentially infinite number of conjunctive queries. Hence, 24] considered how to answer queries given an infinite number of conjunctive source descriptions. Several authors have considered the problem of rewriting queries using views for query optimization [32,6,30]. In this context, one usually requires a query plan that is equivalent to the original query. The algorithms described in [6,30] also explain how to combine the search for query plans with a traditional System R style query optimizer. Another use of rewriting queries using views is explored in ....

[Article contains additional citation context not shown here]

O. G. Tsatalos, M. H. Solomon, and Y. E. Ioannidis. The GMAP: A versatile tool for physical data independence. VLDB Journal, 5(2):101--118, 1996.

....attempts to apply different search paradigms. As we stated in the introduction, one of the reasons for the existence of limited access patterns is the mismatch between the logical and physical views of the data. In our work, binding patterns were used to describe such mismatches. Tsatalos et al. [17] describe GMAPs which are also a mechanism for describing different storage patterns of the data. Using GMAPs, one can describe storage structures in which the stored data is a result of projections, selections and joins on the logical schema of the data, e.g. secondary indexes, path indexes and ....

....on the logical schema of the data, e.g. secondary indexes, path indexes and field replication. GMAPs and binding patterns characterize disjoint sets of mismatches between the logical and physical views of the data. To combine the two families of mismatches, we need to extend the algorithm of in [17] in several ways. First, as we did here, we need to consider annotated query execution plans. Note that in [17] the execution plans manipulate GMAPs (which can be thought of as materialized views) rather than database relations. Second, the join enumeration algorithm needs to consider a plans of ....

[Article contains additional citation context not shown here]

O. G. Tsatalos, M. H. Solomon, and Y. E. Ioannidis. The GMAP: A versatile tool for physical data independence. VLDB Journal, 5(2), 1996.

....physical schema is computed automatically from these specifications and logical operations are mapped to physical operations. Other approaches for physical OODB design include Lanzelotte s work on OODB query optimization [13] which is based on a graph physical design language, and the GMAP system [22] that uses a search based algorithm to match for applicable access paths in a query. 8 Conclusion Object oriented database systems have long been criticized for not supporting sufficient levels of data independence. The main reason for this criticism is that early OODB systems used simple pointer ....

O. Tsatalos, M. Solomon, and Y. Ioannidis. The GMAP: A Versatile Tool for Physical Data Independence. In Proceedings of the 20th VLDB Conference, Santiago, Chile, September 1994.

....is to decide whether in any minimal fixpoint model of a set of Horn rules the extension of one predicate contains the extension of another. The problem has been extensively considered in database theory because it is an important technique for query optimization [34, 29] and related problems [21, 18, 33, 35]. Formally, given a set of Horn rules R and a (finite) set of ground facts G, we can entail a (finite) set of ground atomic facts for every predicate P 2 R. We denote by P R (G) the set of tuples a, such that R [ G j= P ( a) If P is a proposition, i.e. a predicate of arity 0, then P R (G) ....

Odysseas G. Tsatalos, Marvin H. Solomon, and Yannis E. Ioannidis. The GMAP: A versatile tool for physical data independence. VLDB Journal, 5(2):101--118, 1996.

....to the binding pattern limitations on the relations. We before we begin our discussion, we note several closely related problems that are not treated in this paper. As we noted earlier, binding patterns are a method for providing the query optimizer explicit descriptions of the data storage. GMAPs [16, 17] are also a method for describing storage structures. The focus of GMAPs is on describing groupings of the data in a data structure rather than describing limited access patterns to the data. In Section 8 we discuss how these two disjoint classes of storage descriptions can be combined. We noted ....

....attempts to apply different search paradigms. As we stated in the introduction, one of the reasons for the existence of limited access patterns is the mismatch between the logical and physical views of the data. In our work, binding patterns were used to describe such mismatches. Tsatalos et al. [17] describe GMAPs which are also a mechanism for describing different storage patterns of the data. Using GMAPs, one can describe storage structures in which the stored data is a result of projections, selections and joins on the logical schema of the data. For example, using GMAPs it is possible to ....

[Article contains additional citation context not shown here]

Odysseas G. Tsatalos, Marvin H. Solomon, and Yannis E. Ioannidis. The GMAP: A versatile tool for physical data independence. VLDB Journal, 5(2):101--118, 1996.

....to the binding pattern limitations on the relations. We before we begin our discussion, we note several closely related problems that are not treated in this paper. As we noted earlier, binding patterns are a method for providing the query optimizer explicit descriptions of the data storage. GMAPs [16, 17] are also a method for describing storage structures. The focus of GMAPs is on describing groupings of the data in a data structure rather than describing limited access patterns to the data. In Section 8 we discuss how these two disjoint classes of storage descriptions can be combined. We noted ....

Odysseas G. Tsatalos, Marvin H. Solomon, and Yannis E. Ioannidis. The GMAP: A versatile tool for physical data independence. In Proc. of the Int. Conf. on Very Large Data Bases (VLDB), pages 367--378, Santiago, Chile, 1994.

....level in terms of queries (materialized views) over the base extents stored in the database. These queries describe (potentially redundant) configurations of the data itself, access support relations, and materialized functions. A discussion of the relevant issues can be found in [Sch93] or [TSI94] where similar approaches are proposed. Due to lack of space we focus on vertical decomposition as one option for physical design. The monoid calculus can represent the common physical data structures that are prominent in database research today, but decomposition suffices to illustrate the ....

Odysseas G. Tsatalos, Marvin H. Solomon, and Yannis E. Ioannidis. The GMAP: A Versatile Tool for Physical Data Independence. In Proceedings of the 20th Int'l Conference on Very Large Databases (VLDB), pages 367--378, Santiago, Chile, September 1994.

No context found.

O. G. Tsatalos, M. H. Solomon, and Y. E. Ioannidis. The GMAP: A versatile tool for physical data independence. In Proc. VLDB, 1994.

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O. G. Tsatalos, M. H. Solomon, and Y. E. Ioannidis. The GMAP: A versatile tool for physical data independence. VLDB Journal, 5(2):101--118, 1996.

No context found.

Odysseas G. Tsatalos, Marvin H. Solomon, and Yannis E. Ioannidis. The GMAP: A versatile tool for physical data independence. VLDB Journal, 5(2):101-118, 1996.

No context found.

Odysseas G. Tsatalos, Marvin H. Solomon, and Yannis E. Ioannidis. The GMAP: A versatile tool for physical data independence. VLDB Journal, 5(2):101--118, 1996.

No context found.

Odysseas G. Tsatalos, Marvin H. Solomon, and Yannis E. Ioannidis. The GMAP: A versatile tool for physical data independence. VLDB Journal, 5(2):101-118, 1996.

No context found.

Odysseas G. Tsatalos, Marvin H. Solomon, and Yannis E. Ioannidis. The GMAP: A versatile tool for physical data independence. In Proc. of VLDB, pages 367-378, Santiago, Chile, 1994.

No context found.

O. G. Tsatalos, M. H. Solomon, and Y. E. Ioannidis. The GMAP: A versatile tool for physical data independence. VLDB Journal, 5(2):101-118, 1996.

No context found.

O. Tsatalos, M. Solomon, and Y. Ioannidis. The GMAP: A Versatile Tool for Physical Data Independence. VLDB Journal, 5(2), April 1996.

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References 27 Tsatalos, O. G., Solomon, M. H., and Ioannidis, Y. E. (1996). The GMAP: A versatile tool for physical data independence. VLDB Journal, 5(2):101-118.

No context found.

O. G. Tsatalos, M. H. Solomon, and Y. E. Ioannidis. The GMAP: A versatile tool for physical data independence. VLDB Journal, 5(2):101--118, 1996.

No context found.

Tsatalos, Odysseas G.; Solomon, Marvin H.; Ioannidis, Yannis E.; 1994; "The GMAP: A Versatile Tool for Physical Data Independence"; VLDB'94

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