An external taxonomy from which all the descendant term elements are drawn may be referred to using the target attribute.
<elementSpec ident="termList" module="MEI.header">
<desc xml:lang="en">Collection of text phrases which describe a resource.</desc>
<classes>
<memberOf key="att.common"/>
<memberOf key="att.bibl"/>
<memberOf key="att.pointing"/>
</classes>
<constraintSpec ident="checkTermListLabels" scheme="schematron">
<constraint>
<sch:rule context="mei:termList[mei:label]">
<sch:assert role="warning" test="count(mei:label) = count(mei:term)">When labels are used,
usually each term has one.</sch:assert>
</sch:rule>
</constraint>
</constraintSpec>
<remarks xml:lang="en">
<p>An external taxonomy from which all the descendant <gi scheme="MEI">term</gi> elements are
drawn may be referred to using the <att>target</att> attribute.</p>
</remarks>
</elementSpec>