Cyc uses logical reasoning, pulled from a massive knowledge bank which has been growing since 1984 when the project started. Although progress has been slow, it is currently able to produce enough value to pay for itself in applications where decisions must be clearly justified, such as health care and justice. (see homepage)
From Wikipedia: "The Cyc inference engine performs general logical deduction.[8] It also performs inductive reasoning, statistical machine learning and symbolic machine learning, and abductive reasoning. The Cyc inference engine separates the epistemological problem from the heuristic problem. For the latter, Cyc used a community-of-agents architecture in which specialized modules, each with its own algorithm, became prioritized if they could make progress on the sub-problem."
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