2D Z-string: A new spatial knowledge representation for image databases

The knowledge structure called the 2D Cþ-string, proposed by Huang et al., to represent symbolic pictures allows a natural way to construct iconic indexes for images. According to the cutting mechanism of the 2D Cþ-string, an object may be partitioned into several subparts. The number of partitioned subparts is bounded to OðnÞ, where n is the number of objects in the image. Hence, the string length is also bounded to OðnÞ. In this paper, we propose a new spatial knowledge representation called the 2D Z-string. Since there are no cuttings between objects in the 2D Z-string, the integrity of objects is preserved and the string length is bounded to OðnÞ. Finally, some experiments are conducted to compare the performance of both approaches. 2003 Elsevier B.V. All rights reserved.