The Rectangular Attribute Cardinality Map (R-ACM) is a new histogram-like approximation strategy that aims to approximate the density of the underlying attribute values using the philosophies of numerical integration. Analytically, it is shown that for the R-ACM, the distribution of an attribute value within the sector is Binomially distributed. Theoretical results show that the R-ACM scheme is much more accurate than the traditional histograms for query result size estimation.

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Conference Proceedings of the 1999 International Database Engineering and Application Symposium, IDEAS'99
Oommen, J, & Thiyagarajah, Murali (Murali). (1999). Query result size estimation using a novel histogram-like technique: the rectangular attribute cardinality map. Proceedings of the International Database Engineering and Applications Symposium, IDEAS, 3–15.