6.2 Component Predicates

predicate
(resource? val) → boolean?
val : any/c

A resource is identified by a URI, and so this test effectively ensures that val is an absolute URI.

predicate
(subject? val) → boolean?
val : any/c

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
(object? val) → boolean?
val : any/c

A statement’s object may be either a resource?, blank-node?, or a literal?.