Kaizheng Du

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Enric Llurda

Universitat de Lleida

Bent Flyvbjerg

University of Oxford

Remo Caponi

University of Cologne

Valentino Cattelan

Birmingham City University

Andrew W Wilkins

Goldsmiths, University of London

Johannes Preiser-Kapeller

Austrian Academy of Sciences

Aftab Hameed Memon

QUEST Engineering University Nawabshah, Sindh, Pakistan

Mary Ebejer

Western Michigan University

Rogelio Altez

Universidad de Sevilla

Armando Marques-Guedes

UNL - New University of Lisbon

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On automated query modification techniques for databases

In many cases, in order to satisfy certain constraints specified in a database query, the query n... more In many cases, in order to satisfy certain constraints specified in a database query, the query needs to be modified. However, users' "manual" modification is an extra burden on users and, sometimes, may not be correct when users lack knowledge about the database. In a real-time environment, users' manual modification may be too slow to make a query satisfy a given time dead-line. In this thesis, a general automated database query modification model is proposed for automatically modifying database queries with constraints. Five types of query modification constraints, namely, time constraints, error constraints, aggregate function constraints, PCF constraints and count proportionality constraints are introduced. To enable query modification to be performed automatically, two query modification protocols, namely, the use of superset/subset chains based on relation fragmentation and the use of sampling data, are specified. Based on the two query modification protocol...

On Estimators for Aggregate Relational Algebra Queries

Journal of Database Management, 1997

CASE-DB is a relational database management system that allows users to specify time constraints ... more CASE-DB is a relational database management system that allows users to specify time constraints in queries. For an aggregate query AGG(E) where AGG is one of COUNT, SUM and AVERAGE, and E is a relational algebra expression, CASE-DB uses statistical estimators to approximate the query. This paper extends our earlier work on statistical estimators of CASE-DB with the following features: (a) New statistical estimators for COUNT queries with projection. (b) Extending the methodology for SUM and AVERAGE aggregate queries. (c) New sampling plans based on systematic sampling and strati ed sampling. We also present performance evaluation experiments of the estimators with the above extensions using correlated and uncorrelated database instances.

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On Estimating COUNT, SUM, and AVERAGE

Database and Expert Systems Applications, 1991

Modifying database queries and error constraints

Lecture Notes in Computer Science, 1993

In many cases, in order to satisfy constraints on a database query, the query needs to be modifie... more In many cases, in order to satisfy constraints on a database query, the query needs to be modified. However, users' "manual" modification is an extra burden on users and, sometimes may not be correct when users lack knowledge about the database. In this paper, we discuss automated query modification techniques when modification of queries are accompanied by error constraints. We introduce an automated query modification mechanism based on superset/subset and sampling modification protocols.

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On Estimating COUNT, SUM, and AVERAGE Relational Algebra Queries

Database and Expert Systems Applications, 1991

CASE-DB is a relational database management system that allows users to specify time constraints ... more CASE-DB is a relational database management system that allows users to specify time constraints in queries. For an aggregate query AGG(E) where AGG is one of COUNT, SUM and AVERAGE, and E is a relational algebra expression, CASE-DB uses statistical estimators to approximate the query. This paper extends our earlier work on statistical estimators of CASE-DB with the following features: (a) New statistical estimators for COUNT queries with projection, (b) Extending the methodology for SUM and AVERAGE aggregate queries, (c) New sampling plans based on systematic sampling and stratified sampling. We also present performance evaluation experiments of the estimators with the above extensions using artificial database instances.

Time-constrained query processing in CASE-DB

IEEE Transactions on Knowledge and Data Engineering, 1995

CASE-DB is a real-time, single-user, relational prototype DBMS that permits the speci cation of s... more CASE-DB is a real-time, single-user, relational prototype DBMS that permits the speci cation of strict time constraints for relational algebra queries. Given a time constrained non-aggregate relational algebra query and a \fragment chain" for each relation involved in the query, CASE-DB initially obtains a response to a modi ed version of the query and then uses an \iterative query evaluation" technique to successively improve and evaluate the modi ed version of the query. CASE-DB controls the risk of overspending the time quota at each step using a \risk control technique".

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Processing real-time, non-aggregate queries with time-constraints in CASE-DB

[1992] Eighth International Conference on Data Engineering

... Time-Constraints in CASE-DBt Gultekin Ozsoyogluf Kaizheng Dui, Sujatha Guru swaniyi, Well-Chi... more ... Time-Constraints in CASE-DBt Gultekin Ozsoyogluf Kaizheng Dui, Sujatha Guru swaniyi, Well-Chi Hout ... Pleast, note that, in the algorit.lim in figure 2, there is a trailsforination of the modified query Qs into Q: siich t.1ia.t. Q: uses “the previous st.ep&amp;#39;s response”. The first. ...

On automated query modification techniques for databases

On Estimators for Aggregate Relational Algebra Queries

Journal of Database Management, 1997

Download

On Estimating COUNT, SUM, and AVERAGE

Database and Expert Systems Applications, 1991

Modifying database queries and error constraints

Lecture Notes in Computer Science, 1993

Download

On Estimating COUNT, SUM, and AVERAGE Relational Algebra Queries

Database and Expert Systems Applications, 1991

CASE-DB is a relational database management system that allows users to specify time constraints ... more CASE-DB is a relational database management system that allows users to specify time constraints in queries. For an aggregate query AGG(E) where AGG is one of COUNT, SUM and AVERAGE, and E is a relational algebra expression, CASE-DB uses statistical estimators to approximate the query. This paper extends our earlier work on statistical estimators of CASE-DB with the following features: (a) New statistical estimators for COUNT queries with projection, (b) Extending the methodology for SUM and AVERAGE aggregate queries, (c) New sampling plans based on systematic sampling and stratified sampling. We also present performance evaluation experiments of the estimators with the above extensions using artificial database instances.

Time-constrained query processing in CASE-DB

IEEE Transactions on Knowledge and Data Engineering, 1995

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Processing real-time, non-aggregate queries with time-constraints in CASE-DB

[1992] Eighth International Conference on Data Engineering

Kaizheng Du

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