US Patent 8010560 Abducing assertion to support access query

Logical abduction is used to derive the premises that support an access query. In a logic-based access-control system, a query, as to one or more principals' right to access one or more resources, is a statement that can be either true or false. The statement evaluates to true if the principal is allowed to access the resource under the existing set of assertions. Assertions that, if made, would cause the statement to be true can be abduced from the query and from the policy against which the truth of the query is to be judged. The abduced assertions can be used to assist in making the appropriate assertions to cause the query to evaluate to true so that access to the resource can be granted.