<label>is the name of the rule. It can be a single word or a string (enclosed by double brackets). It is followed by a colon (
:) to distinguish the label from the concept that follows.
<Concept>is the name of the Concept for atoms of which the rule specifies an identity
<Concept>. This is enforced by the type system.
ssn, but also by the combination of
birthdate. This statement can also be used to objectify (reify) an term