<class>:<key> : string representation of an ObjectIdentifier.
OR:<class>:<key> : string representation of an ObjectReference.
VR:<class>:<key> : string representation of an VersionReference.
Snippets:
/* ObjectIdentifier string to WTPart */
ObjectIdentifier oid = ObjectIdentifier.newObjectIdentifier("wt.part.WTPart:20154");
WTPart part = (WTPart) PersistenceHelper.manager.refresh(oid);
/* ObjectReference / VersionReference string to WTPart */
ReferenceFactory rf = new ReferenceFactory();
WTReference ref = (WTReference) rf.getReference("OR:wt.part.WTPart:20154");
WTPartpart = (WTPart) ref.getObject();
ReferenceFactory rf = new ReferenceFactory();
WTReference ref = (WTReference) rf.getReference("VR:wt.part.WTPart:20153");
WTPart part = (WTPart) ref.getObject();