A Raster Approximation for the Processing of Spatial Joins

The processing of spatial joins can be greatly improved by the use of filters that reduce the need for examining the exact geometry of polygons in order to find the intersecting ones. Approximations of candidate pairs of polygons are examined using such filters. As a result, three possible sets of answers are identified: the positive one, composed of intersecting polygon pairs; the negative one, composed of nonintersecting polygon pairs; and the inconclusive one, composed of the remaining pairs of candidates. To identify all the intersecting pairs of polygons with inconclusive answers, it is necessary to have access to the representation of polygons so that an exact geometry test can take place. This article presents a polygon approximation for spatial join processing which we call four-colors raster signature (4CRS). The performance of a filter using this approximation was evaluated with real world data sets. The results showed that our approach, when compared to ..

DWFIST

This chapter presents the core of the DWFIST approach, which is concerned with supporting the analysis and exploration of frequent itemsets and derived patterns, e.g., association rules in transactional datasets. The goal of this new approach is to provide: (1) flexible pattern-retrieval capabilities without requiring the original data during the analysis phase; and (2) a standard modeling for data warehouses of frequent itemsets, allowing an easier development and reuse of tools for analysis and exploration of itemset-based patterns. Instead of storing the original datasets, our approach organizes frequent itemsets holding on different partitions of the original transactions in a data warehouse that retains sufficient information for future analysis. A running example for mining calendar-based patterns on data streams is presented. Staging area tasks are discussed and standard conceptual and logical schemas are presented. Properties of this standard modeling allow retrieval of frequent itemsets holding on any set of partitions, along with upper and lower bounds on their frequency counts. Furthermore, precision guarantees for some interestingness measures of association rules are provided as well. </jats:p