Incomplete data and data dependencies in relational databases
By: Sergio Greco, Cristian Molinaro, and Francesca Spezzano
Contributors: Molinaro, Cristian; Spezzano, Francesca
Series: Synthesis lectures on data management -- #29; Synthesis lectures on data management -- #29.
Publisher: Morgan & Claypool
Published: 2012
Place of publication: San Rafael, Calif. (1537 Fourth Street, San Rafael, CA 94901 USA)
Language: eng
Number of pages: 111
ISBN-13: 9781608459278; 9781608459261
Subjects: Relational databases; Querying (Computer science); Data mining; Database design; COMPUTERS; Programming Languages; SQL
Description: The chase has long been used as a central tool to analyze dependencies and their effect on queries. It has been applied to different relevant problems in database theory such as query optimization, query containment and equivalence, dependency implication, and database schema design. Recent years have seen a renewed interest in the chase as an important tool in several database applications, such as data exchange and integration, query answering in incomplete data, and many others. It is well known that the chase algorithm might be non-terminating and thus, in order for it to find practical applicability, it is crucial to identify cases where its termination is guaranteed. Another important aspect to consider when dealing with the chase is that it can introduce null values into the database, thereby leading to incomplete data. Thus, in several scenarios where the chase is used the problem of dealing with data dependencies and incomplete data arises. This book discusses fundamental issues concerning data dependencies and incomplete data with a particular focus on the chase and its applications in different database areas. We report recent results about the crucial issue of identifying conditions that guarantee the chase termination. Different database applications where the chase is a central tool are discussed with particular attention devoted to query answering in the presence of data dependencies and database schema design.
Notes: Includes bibliographical references (pages 97-110).

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Table of contents: title: 1. Introduction.; title: 2. Relational databases; title: 2.1 Relational model; title: 2.2 Query languages; title: 2.2.1 Relational algebra; title: 2.2.2 Relational calculus; title: 2.2.3 Domain independent and safe RC queries; title: 2.2.4 Datalog; title: 2.3 Conjunctive queries.; title: 3. Incomplete databases; title: 3.1 Incomplete databases; title: 3.2 Representation systems; title: 3.3 Nulls in SQL.; title: 4. The chase algorithm; title: 4.1 Data dependencies; title: 4.2 Universal solutions and query answers; title: 4.3 Dependency skolemization; title: 4.4 Standard chase algorithm; title: 4.5 Oblivious chase; title: 4.6 Core chase; title: 4.7 Comparison among chase algorithms.; title: 5. Chase termination; title: 5.1 Chase termination criteria; title: 5.2 Relationship among chase termination conditions; title: 5.3 Constraint rewriting.; title: 6. Data dependencies and normal forms; title: 6.1 Basic notations and terminology; title: 6.2 Functional dependencies; title: 6.3 Multivalued dependencies; title: 6.4 Join dependencies; title: 6.5 Decompositions; title: 6.6 Normal forms; title: 6.7 Chasing with FDs and JDs.; title: 7. Universal repairs; title: 7.1 Universal repairs; title: 7.2 Special classes of dependencies; title: 7.2.1 LAV; title: 7.2.2 GAV; title: 7.2.3 Terminating dependencies.; title: 8. Chase and database applications; title: 8.1 Query containment under constraints; title: 8.2 Query optimization; title: 8.3 Data exchange; title: 8.4 Data integration; title: 8.5 Query answering on incomplete data.; title: Bibliography; title: Authors' biographies.