ERN-4 PartyList

The Party List allows that recipients of ERN-4 formatted messages will be able to clearly determine, where two sound recordings in the same message list the artist as John Williams, whether it is the same John Williams on both sound recordings or whether each sound recording was created by two different John Williams. 

ERN-3

<!-- In 1st Sound Recording -->
<ResourceContributor>
  <PartyName>
    <FullName>John Williams</FullName>
  </PartyName>
  ...
</ResourceContributor>
  
<!-- In 2nd Sound Recording -->
<ResourceContributor>
  <PartyName>
    <FullName>John Williams</FullName>
  </PartyName>
  ...
</ResourceContributor>

ERN-4 (Two John Williamses)

<!-- In 1st Sound Recording -->
<Contributor>
  <ContributorPartyReference>
    P101
  </ContributorPartyReference>
  ...
</Contributor>
 
<!-- In 2nd Sound Recording -->
<Contributor>
  <ContributorPartyReference>
    P202
  </ContributorPartyReference>
  ...
</Contributor>

ERN-4 (One John Williams)

<!-- In 1st Sound Recording -->
<Contributor>
  <ContributorPartyReference>
    P101
  </ContributorPartyReference>
  ...
</Contributor>
 
<!-- In 2nd Sound Recording -->
<Contributor>
  <ContributorPartyReference>
    P101
  </ContributorPartyReference>
  ...
</Contributor>

The two ERN-4 examples will be even more powerful when the parties' names are augmented by identifiers:

<Party>
    <PartyReference>P101</PartyReference>
    <PartyName>
        <FullName>
            John Williams
        </FullName>
    </PartyName>
    <PartyId>
        <ISNI>0000 0000 4587 1863</ISNI>
    </PartyId>
</Party>

<Party>
    <PartyReference>P101</PartyReference>
    <PartyName>
        <FullName>
            John Williams
        </FullName>
    </PartyName>
    <PartyId>
        <ISNI>0000 0000 4587 1863</ISNI>
    </PartyId>
</Party>

<Party>
    <PartyReference>P202</PartyReference>
    <PartyName>
        <FullName>
            John Williams
        </FullName>
    </PartyName>
    <PartyId>
        <ISNI>0000 0000 3846 1225</ISNI>
    </PartyId>
</Party>