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ACM Transactions on Information Systems (TOIS), Volume 17 Issue 2, April 1999

A flexible authorization mechanism for relational data management systems
Elisa Bertino, Sushil Jajodia, Pierangela Samarati
Pages: 101-140
DOI: 10.1145/306686.306687
In this article, we present an authorization model that can be used to express a number of discretionary access control policies for relational data management systems. The model permits both positive and negative authorizations and supports...

Context-sensitive learning methods for text categorization
William W. Cohen, Yoram Singer
Pages: 141-173
DOI: 10.1145/306686.306688
Two recently implemented machine-learning algorithms, RIPPERand sleeping-experts for phrases, are evaluated on a number of large text categorization problems. These algorithms both construct classifiers that...

A robust framework for content-based retrieval by spatial similarity in image databases
Essam A. El-Kwae, Mansur R. Kabuka
Pages: 174-198
DOI: 10.1145/306686.306689
A framework for retrieving images by spatial similarity (FRISS) in ima ge databases is presented. In this framework, a robust retrieval by spatial similarity (RSS) algorithm is defined as one that incorporates both directional and topological...

Incremental formalization with the hyper-object substrate
Frank M. Shipman, III, Raymond J. McCall
Pages: 199-227
DOI: 10.1145/306686.306690
Computers require formally represented information to perform computations that support users; yet users who have needed such support have often proved to be unable or unwilling to formalize it. To address this problem, this article introduces...