Identifier for parties in a demographic or identity service. There are typically a
number of subtypes of the PARTY class, including PERSON, ORGANISATION, etc.
Abstract supertypes are allowed if the referenced object is of a type not known by
the current implementation of this class (in other words, if the demographic model
is changed by the addition of a new PARTY or ACTOR subtypes, valid
PARTY_REFs can still be constructed to them).
Declaration :
Artifact : PARTY_REF