A simple example

<!ELEMENT text (#PCDATA|emph|name)*>
<!ATTLIST text
       timestamp NMTOKEN #REQUIRED>

---

<xs:element name="text">
 <xs:complexType content="mixed">
  <xs:choice minOccurs="0" maxOccurs="unbounded">
   <xs:element ref="emph"/>
   <xs:element ref="name"/> 
  </xs:choice> 
  <xs:attribute name="timestamp" type="date" minOccurs="1"/>
 </xs:complexType>
</xs:element>