[1] RDF Schema 1.1 ( (2/27/2014, 12:42:23 PM 版)) <https://dvcs.w3.org/hg/rdf/raw-file/default/rdf-schema/index.html#h4_ch_object>
[2] RDF 1.1 Concepts and Abstract Syntax ( (4/25/2014, 8:28:00 PM 版)) <https://dvcs.w3.org/hg/rdf/raw-file/default/rdf-concepts/index.html#dfn-object>
Google search: object