Asserts that this observation FDO records a measured, predicted, or recorded property of the referent identified by the object URI. Used by Types 2–8 to link each observation to the central anchor FDO of the FAIR Digital Twin, making the anchor the hub of the knowlet topology. The object URI is the referent URI (i.e., the `sub:fdo` identifier declared by the anchor nanopublication), not the Trusty URI of the anchor itself.