Combining C-signature with Path Dictionary for Query Processing of Nested Objects in OODBS

Abstract

Since an object-oriented database system (OODBS) dealing with composite objects requires expensive traversal costs to process user queries, query processing and indexing have become important issues in the success of object-oriented database systems. In this paper, we propose a new signaturebased indexing scheme entitled c-signature. The c-signatures are abstracted from objects in a path in concatenation and are stored in a class-oriented way, so as to reduce search space. By positioning the c-signature file before the path dictionary, we can avoid expensive scanning of the database. Also, the csignatures pointing to an s-expression in the path dictionary make it possible to avoid the sequential scanning of the path dictionary. Based on the proposed scheme, we develop implement the c-signature and its competitors such as path index, path signature, path dictionary, class unit signature, path dictionary index, and s-signature schemes. Using the experimental results, we compare the c-signature with the competitors under different degrees of reference sharing and in terms of the page I/Os of each scheme. Finally, we show that our csignature scheme achieves significant improvements in the retrieval operation.