recursion with an except.

I have a definition of a bunch of inlines.

<define name="Inline.group">
  <choice>
    <text/>
    <ref name="Em"/>
    <ref name="Strong"/>
    <ref name="Dfn"/>
    <ref name="Code"/>
    <ref name="Samp"/>
    <ref name="Kbd"/>
    <ref name="Cite"/>
    <ref name="Abbr"/>
    <ref name="Acronym"/>

etc.

I want to exclude recursion, say in the em element

<define name="Em">
<element name="em">
<ref name="Inline.group">
  <except>
    <ref name="Em"/>
  </except>
</ref>
</element>
</define>

Seemed about right, but jing tells me
inlines.rng:120: error: found "except" element but expected empty content

Is it necessary to list out all the elements,
making the definition redundant? 
  Since its mixed content, I'm unsure if this is possible anyway,
from the Inline.group definition.

Any suggestions please?
  TIA, DaveP

 



Regards DaveP.

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