A ground sentence contains no variables.
(<=> (Ground-Sentence ?Expression)
(And (Sentence ?Expression)
(Value-Type ?Expression Variables-In-Sentence Empty)
(Value-Cardinality ?Expression Variables-In-Sentence 1)))
(Sentence ?Expression)
(Inherited-Facet-Value Slot-Value-Type
Parametric-Constraint
Constraint.Expression
Ground-Sentence)
(<=> (Parametric-Constraint ?Constraint)
(And (Constraint ?Constraint)
(Value-Type ?Constraint
Constraint.Expression
Ground-Sentence)
(Value-Cardinality ?Constraint Constraint.Expression 1)))
(<=> (Ground-Sentence ?Expression)
(And (Sentence ?Expression)
(Value-Type ?Expression Variables-In-Sentence Empty)
(Value-Cardinality ?Expression Variables-In-Sentence 1)))