Validate that URI is not empty in RelaxNG

Question

I'm trying to validate that an element always has an href attribute in RelaxNG, and assumed you could do it with this:

<attribute name="href">
  <data type="anyURI"/>
</attribute>

Only catch is, apparently anyURI considers empty strings to be valid, so href="" passes with flying colors. Is there any easy way to fix this?

Answer 1

You can use the minLength facet. For example:

<attribute name="href">
  <data type="anyURI">
    <param name="minLength">5</param>
  </data>
</attribute>

See also http://www.w3.org/TR/xmlschema-2/#anyURI