 special considerations: (1) when an IRI that is not also a URI is
          given for dereferencing, it MUST be mapped to a URI using the steps in
          Section 3.1 of [[!RFC3987]] and (2) when an IRI is serving as an "id"
          value, it MUST NOT be so mapped.
        </p>

        <p>
          Relative IRI (and URL) references SHOULD NOT be used within an
          Activity Streams 2.0 document due to the fact that many JSON
          parser implementations are not capable of reliably preserving