<NOT> element is an access control operator that reverses the result of a single nested rule or operator, meaning it is satisfied if and only if its child is not.
One (and only one) of the following elements can appear:
- A single access rule to enforce.
- A single regular expression access rule to enforce.
- An operator for combining any number of rules or operators with a disjunction.
- An operator for combining any number of rules or operators with a conjunction.
- An operator for reversing the meaning of a single rule or operator.