I'm trying to view track composer relationships through /ws/1, for some legacy software that hasn't been migrated. Including inc=artist-rels includes some relations, but not the composer one. e.g.
http://classic.musicbrainz.org/ws/1/track/0e04d324-4710-422e-8a4a-1d7362caa5ad?type=xml&inc=artist+artist-rels shows

<metadata xmlns="http://musicbrainz.org/ns/mmd-1.0#">
<track id="0e04d324-4710-422e-8a4a-1d7362caa5ad">
<title>I Saw Her Standing There</title>
<duration>178000</duration>
<artist id="b10bbbfc-cf9e-42e0-be17-e2c3e1d2600d" type="Group">
<name>The Beatles</name>
<sort-name>Beatles, The</sort-name>
<life-span begin="1957" end="1970-04-10"/>
</artist>
<relation-list target-type="Artist">
<relation type="Vocal" attributes="Lead" target="ba550d0e-adac-4864-b88b-407cab5e76af" begin="" end="">
<artist id="ba550d0e-adac-4864-b88b-407cab5e76af" type="Person">
<name>Paul McCartney</name>
<sort-name>McCartney, Paul</sort-name>
<life-span begin="1942-06-18"/>
</artist>
</relation>
<relation type="Composer" target="ba550d0e-adac-4864-b88b-407cab5e76af" begin="" end="">
<artist id="ba550d0e-adac-4864-b88b-407cab5e76af" type="Person">
<name>Paul McCartney</name>
<sort-name>McCartney, Paul</sort-name>
<life-span begin="1942-06-18"/>
</artist>
</relation>
<relation type="Composer" target="4d5447d7-c61c-4120-ba1b-d7f471d385b9" begin="" end="">
<artist id="4d5447d7-c61c-4120-ba1b-d7f471d385b9" type="Person">
<name>John Lennon</name>
<sort-name>Lennon, John</sort-name>
<life-span begin="1940-10-09" end="1980-12-08"/>
</artist>
</relation>
</relation-list>
</track>
</metadata>

While the same query to http://musicbrainz.org/ws/1/track/0e04d324-4710-422e-8a4a-1d7362caa5ad?type=xml&inc=artist+artist-rels gives

<metadata xmlns="http://musicbrainz.org/ns/mmd-1.0#">
<track id="0e04d324-4710-422e-8a4a-1d7362caa5ad">
<title>I Saw Her Standing There</title>
<duration>178000</duration>
<artist id="b10bbbfc-cf9e-42e0-be17-e2c3e1d2600d">
<name>The Beatles</name>
<sort-name>Beatles, The</sort-name>
</artist>
<relation-list target-type="Artist">
<relation direction="backward" target="ba550d0e-adac-4864-b88b-407cab5e76af" type="Vocal" attributes="Lead">
<artist id="ba550d0e-adac-4864-b88b-407cab5e76af">
<name>Paul McCartney</name>
<sort-name>McCartney, Paul</sort-name>
<life-span begin="1942-06-18"/>
</artist>
</relation>
</relation-list>
</track>
</metadata>

The vocal relation is showing, but not the composer ones