An organization identifier as defined in ISO 6523(-1). Note that many existing organization identifiers such as <a href="https://schema.org/leiCode">leiCode</a>, <a href="https://schema.org/duns">duns</a> and <a href="https://schema.org/vatID">vatID</a> can be expressed as an ISO 6523 identifier by setting the ICD part of the ISO 6523 identifier accordingly.