Validation: Relax-NG

• Relax-NG: Counter proposal to Schemas structures
• Very flexible, clear, formal definition
• Allow to reuse external Datatypes
• Fully implemented in libxml2
• Developped by OASIS, on standard track at ISO

<element name="p"
   xmlns="http://relaxng.org/ns/structure/1.0">
  <zeroOrMore>
    <choice>
      <text/>
      <element name="a">
        <attribute name="href"/>
        <text/>
      </element>
    </choice>
  </zeroOrMore>
</element>

See example 4, XML, RNG