Lazy Aggregates for Real-Time OLAP

In OLAP models, or data cubes, aggregates have to be recalculated when the underlying base data changes. This may cause performance problems in real-time OLAP systems, which continuously accommodate huge amounts of measurement data. To optimize the aggregate computations, a new consistency criterion called the tolerance invariant is proposed. Lazy aggregates are aggregates that are recalculated only when the tolerance invariant is violated, i.e., the error of the previously calculated aggregate exceeds the given tolerance. An industrial case study is presented. The prototype implementation is described, together with the performance results.

[1]  Jennifer Widom,et al.  Active Database Systems: Triggers and Rules For Advanced Database Processing , 1994 .

[2]  Johan van Benthem,et al.  The Logic of Time , 1983 .

[3]  Antoni Wolski,et al.  The RAPID Case Study: Requirements for and the Design of a Fast-Response Database System , 1996, RTDB.

[4]  Angelika Kotz Dittrich,et al.  Research perspectives for time series management systems , 1994, SGMD.

[5]  Robert W. Marti,et al.  Time Series, A Neglected Issue in Temporal Database Research? , 1995, Temporal Databases.

[6]  Tomasz Imielinski,et al.  The Relational Model of Data and Cylindric Algebras , 1984, J. Comput. Syst. Sci..

[7]  Jeffrey F. Naughton,et al.  On the Computation of Multidimensional Aggregates , 1996, VLDB.

[8]  Jennifer Widom,et al.  The WHIPS prototype for data warehouse creation and maintenance , 1997, SIGMOD '97.

[9]  Jennifer Widom,et al.  Research problems in data warehousing , 1995, CIKM '95.

[10]  Inderpal Singh Mumick,et al.  Maintenance of data cubes and summary tables in a warehouse , 1997, SIGMOD '97.

[11]  Ramez Elmasri,et al.  An Integrated Temporal Data Model Incorporating Time Series Concept , 1998, Data Knowl. Eng..

[12]  Richard T. Snodgrass,et al.  The temporal query language TQuel , 1987, TODS.

[13]  E. F. Codd,et al.  Providing OLAP to User-Analysts: An IT Mandate , 1998 .

[14]  Jeffrey D. Ullman,et al.  Implementing data cubes efficiently , 1996, SIGMOD '96.

[15]  Antoni Wolski,et al.  Fuzzy triggers: incorporating imprecise reasoning into active databases , 1998, Proceedings 14th International Conference on Data Engineering.

[16]  M. Tamer Özsu,et al.  Temporal Extensions to a Uniform Behavioral Object Model , 1993, ER.

[17]  Mark Sullivan,et al.  Quasi-cubes: exploiting approximations in multidimensional databases , 1997, SGMD.