18. The one or more computer-readable storage media as recited in claim 13 , wherein the first level comprises an assertion level that is populated by assertions, wherein the second level comprises a query level that is populated by the authorization queries formed at least from the asserted facts, and wherein the bifurcated security scheme evaluates a particular authorization query by attempting to match validated assertions from the assertion level to one or more asserted facts of the particular authorization query.
13. One or more computer-readable storage media with computer-executable instructions that, when executed on a processor, configure the processor to perform acts comprising: implementing a bifurcated security scheme having a first level and a second level, wherein the first level includes a syntactic validator that disallows an assertion containing a negation and the second level permits usage of negations within an authorization query, and wherein each authorization query is a logical English expression comprising conditions, asserted facts, and/or logical operators.