Constraints - case example

<?xml version="1.0"?>
<RDF xmlns="http://www.w3.org/TR/WD-rdf-syntax#"
     xmlns:rdf="http://www.w3.org/TR/WD-rdf-syntax#"
     xmlns:RDFS="http://www.w3.org/TR/WD-rdf-schema#">

<Class ID="Document" />

<PropertyType ID="language">
  <RDFS:Comment xml:lang="en">Language encoded as a string from ISO 639.</RDFS:Comment>
  <RDFS:Range rdf:resource="http://www.forth.gr/conf/iso639.rdf" />
  <RDFS:Domain rdf:resource="#Document" />
</PropertyType>

<PropertyType ID="country">
  <RDFS:Comment xml:lang="en">Country code encoded as a string from ISO 3166</RDFS:Comment>
  <RDFS:Range rdf:resource="http://www.forth.gr/conf/iso3166.rdf" />
  <RDFS:Domain rdf:resource="#Document" />
</PropertyType>

<PropertyType ID="encoding">
  <RDFS:Comment xml:lang="en">Encoding identifier as a string from set
{ASCII, ISO-8859-1, UTF-8, UCS-2}</RDFS:Comment>
  <RDFS:Range rdf:resource="http://www.forth.gr/conf/encodings.rdf" />
  <RDFS:Domain rdf:resource="#Document" />
</PropertyType>

</RDF>