Approximate Spatial Query Processing using Raster Signatures

Nowadays, the database characteristics, such as the huge volume of data, the complexity of the queries, and even the data availability, can demand minutes or hours to process a query. On the other hand, in many cases it may be enough to the user to get a fast approximate answer, since it has the desired precision. The challenge to give to the user an exact query answer within a reasonable time becomes even bigger in the spatial database field. This work proposes the use of the Four Color Raster Signature (4CRS) for approximate query processing. The main goal is to reduce the time required to process a query executing it on approximate data (4CRS signature) instead of accessing the real datasets. The experimental tests demonstrated the good results of our proposal. Considering the test of the most important algorithm, the time required to process an approximate query answer has average of 7.22% of the time to get an exact answer, the disk accesses have average of 7.04% and the average error is 1% related to exact processing. Besides the 4CRS storage requirements are also quite small, which has an average of only 3.57% of the space required to store the real datasets.