The triple statements are normally represented as graphs with nodes and arcs, where subject and object are nodes, while predicates are arcs (also called edges: the arrows, the relationships). Each combination of node-arc-node is a distinct triple. All components of the triple are ideally identified by URIs, even predicates/arcs (see how these URIs make it possible to embed semantic vocabularies in RDF statements in lesson 4.4. In the figure below, the predicate/arc is the URI of the property as defined in an existing metadata vocabulary which was in turn formalised as RDF, which means all classes and properties have URIs).