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We describe several new bottom-up approaches to problems in role engineering for Role-Based Access Control (RBAC). The salient problems are all NP-complete, even to approximate, yet we find that in instances that arise in practice these problems can be solved in minutes. We first consider role minimization, the process of finding a smallest collection of(More)
The use of tabling in logic programming allows bottom-up evaluation to be incorporated in a top-down framework, combining advantages of both. At the engine level, tabling also introduces issues not present in pure top-down evaluation, due to the need for subgoais and answers to access tables during resolution. This article describes the design,(More)
The well-founded model provides a natural and robust semantics for logic programs with negative literals in rule bodies. We implemented the well-founded semantics in the SLG-WAM of XSB 19]. Performance results indicate that the overhead of delay and simpliica-tion to Prolog | or tabled | evaluations is minimal. To compute the well-founded semantics, the(More)
Tabled resolution improves eeciency as well as termination properties of logic programs by sharing answer computations across sim-ilar" subgoals. Similarity based on subsumption of subgoals rather than variance i.e., identity modulo variable renaming promotes more aggressive sharing, but requires mechanisms to index answers from dynamically growing sets.(More)
The current study sought to test the efficacy and safety of the novel selective norepinephrine reuptake inhibitor LY2216684 compared to placebo in patients with major depressive disorder (MDD). Escitalopram was used as a control for assay sensitivity. Adult outpatients with MDD, confirmed at screening by the Mini International Neuropsychiatric Interview, a(More)
To date (Version 1.7.1), the core engine development of the SLG-WAM has been mainly implemented by Terrance Swift, Kostis Sagonas, Prasad Rao and Juliana Freire. The breakdown, roughly, was that Terrance Swift wrote the initial tabling engine, Prasad Rao wrote the trie-based table access routines, and Kostis Sagonas implemented most of tabled negation.(More)