P5: Guidelines for Electronic Text Encoding and Interchange

<rng:element name="attDef">
<rng:ref name="att.global.attributes"/>
<rng:ref name="att.identified.attributes"/>
<rng:optional>
 <rng:attribute name="usage" a:defaultValue="opt">
  <rng:choice>
   <rng:value>req</rng:value>
   <rng:value>mwa</rng:value>
   <rng:value>rec</rng:value>
   <rng:value>rwa</rng:value>
   <rng:value>opt</rng:value>
  </rng:choice>
 </rng:attribute>
</rng:optional>
<rng:optional>
 <rng:attribute name="ns"
   a:defaultValue="http://www.tei-c.org/ns/1.0">
  <rng:ref name="data.namespace"/>
 </rng:attribute>
</rng:optional>
<rng:group>
 <rng:zeroOrMore>
  <rng:ref name="model.glossLike"/>
 </rng:zeroOrMore>
 <rng:optional>
  <rng:ref name="datatype"/>
 </rng:optional>
 <rng:optional>
  <rng:ref name="defaultVal"/>
 </rng:optional>
 <rng:optional>
  <rng:choice>
   <rng:ref name="valList"/>
   <rng:ref name="valDesc"/>
  </rng:choice>
 </rng:optional>
 <rng:zeroOrMore>
  <rng:ref name="exemplum"/>
 </rng:zeroOrMore>
 <rng:zeroOrMore>
  <rng:ref name="remarks"/>
 </rng:zeroOrMore>
</rng:group>
</rng:element>

element attDef
{
   att.global.attributes,
   att.identified.attributes,
   attribute usage { "req" | "mwa" | "rec" | "rwa" | "opt" }?,
   attribute ns { data.namespace }?,
   (
      model.glossLike*,
      datatype?,
      defaultVal?,
      ( valList | valDesc )?,
      exemplum*,
      remarks*
   )
}