The generated documentation says: "The values of the style:position attribute are left, center, right, top, bottom, one of these values: left, center or right followed by one of these values: top, center or bottom or one of these values: top, center or bottom followed by one of these values: left, center or right."

The schema fragment reads:

<define name="style-background-image-attlist" combine="interleave">
<optional>
<attribute name="style:position">
<choice>
<value>left</value>
<value>center</value>
<value>right</value>
<value>top</value>
<value>bottom</value>
<list>
<ref name="horiBackPos"/>
<ref name="vertBackPos"/>
</list>
<list>
<ref name="vertBackPos"/>
<ref name="horiBackPos"/>
</list>
</choice>
</attribute>
</optional>
</define>

<define name="horiBackPos">
<choice>
<value>left</value>
<value>center</value>
<value>right</value>
</choice>
</define>
<define name="vertBackPos">
<choice>
<value>top</value>
<value>center</value>
<value>bottom</value>
</choice>
</define>

I think it is the use of <choice> versus the description of one value following another that is throwing me. Seems like with <choice> that is what I get, choice, not a multi-part value.