Language Support for Raster Image Manipulation in Databases

Abstract

Multidimensional array data come up in many application areas. In computer graphics and imaging, those — usually 2D — arrays are conceived as raster images; pixel information, then, denotes some color value. In scientific visualization, pixel or voxel information can carry arbitrary semantics, such as temperature, speed, or stress. The size of such structures may well go into Gigabytes per object.

In principle, storage of huge data volumes and flexible retrieval among them is a typical task of database systems. However, current database technology is not prepared to cope with multidimensional arrays of arbitrary size. Hence, if today in visualization database systems are employed at all, they store such data as byte sequences, thereby losing all structure information. As a consequence, it is impossible to extract partial information from one such object, or to use it within a query. Moreover, as structure information is lost, transparent exchange within heterogeneous networks cannot be supported.

This paper describes an approach to the modeling of general arrays of unlimited size in database systems. It is done in a way that the system keeps structure information in the schema, and hence overcomes the previously stated limitations.

As the most prominent case of multidimensional arrays still are raster images, focus here is on the two-dimensional case. The results, however, are valid for any number of dimension.

This work is sponsored by DFN Assoc. (German Research Net Association) under grant no. TK558-VA014