and
Hiroyuki Kitagawa (Institute of Information Science and Electronics, University of Tsukuba)
PS file (9 pages, 411,023 bytes)
IEICE Transactions of Information and Systems, Vol. 78-D, No. 11, pp. 1424-1432, Nov. 1995.
Efficient retrieval of nested objects is an important issue in advanced database systems. So far, a number of indexing methods for nested objects have been proposed. However, they do not consider retrieval of nested objects based on the set comparison operators such as $\supseteq$ and $\subseteq$. Previously, we proposed four set access facilities for nested objects and compared their performance in terms of retrieval cost, storage cost, and update cost. In this paper, we extend the study and present refined algorithms and cost formulas applicable to more generalized situations. Our cost models and analysis not only contribute to the study of set-valued retrieval but also to cost estimation of various indexing methods for nested objects in general.