7.2 Component Predicates
A resource is identified by a URI, and so this test effectively ensures that val is an absolute URI.
A statement’s subject may be a resource? or a blank-node?.
predicate
(predicate? val) → boolean?
val : any/c
A statement’s predicate must be a resource?.
predicate
(predicate<? v1 v2) → boolean?
v1 : predicate? v2 : predicate?