A VT constraint-sentence is a constraint-sentence with the logical operators, relational constants, and attribute operators restricted as listed below.
(=> (Vt-Constraint-Sentence ?Sentence) (Restricted-Constraint-Sentence ?Sentence (One-Of 'And 'Or 'Not '=> '<= '<=>) (One-Of '= '/= '< '> '=< '>= 'Member) Function-Allowed-In-Vt-Constraint Atomic-Term))