EbRIM/identifiers
Every RegistryObject is a persistent identifiable object. Being persistent means it can be stored and later retrieved. Being identifiable means it has a permanent id which can be used to address it. In XML this permanent id is the id attribute:
<ExtrinsicObject id="urn:uuid:14d4debf-8f97-4251-9a74-a90016b0af0d" ...