url ! --&gt;
      &lt;!-- comma separated list of keywords --&gt;
      &lt;xs:element name="keywords"    type="xs:string" minOccurs="0" /&gt;
      &lt;!-- comma separated list of pre-defined categories --&gt;
      &lt;xs:element name="category"    type="xs:string" minOccurs="0" /&gt;
      &lt;!-- license covering the layer (the license of referenced components is not covered) --&gt;
      &lt;xs:element name="license"     type="xs:string" minOccurs="0" /&gt;
    &lt;/xs:all&gt;
    &lt;!-- layer name i