<elementSpec ident="attUsage" module="MEI.header">
<desc xml:lang="en">Documents the usage of a specific attribute of the element.</desc>
<constraintSpec ident="context_attribute_requires_content" scheme="schematron">
<constraint>
<sch:rule context="@context">
<sch:assert role="warning" test="not(normalize-space(.) eq '')">@context attribute should
contain an XPath expression.</sch:assert>
</sch:rule>
</constraint>
</constraintSpec>
<attList>
<attDef ident="name" usage="req">
<desc xml:lang="en">Name of the attribute.</desc>
</attDef>
<attDef ident="context" usage="opt">
<desc xml:lang="en">Circumstances in which the attribute appears, an XPath expression.</desc>
<datatype>
<rng:data type="string"/>
</datatype>
</attDef>
</attList>
</elementSpec>