Namespaces: a key in peer-to-peer architecture (cont.)

We can use an XML namespace to unambiguously identify the Dublin Core vocabulary just pointing to the Dublin Core resources defining its semantics.
An example:

<rdf:RDF
  xmlns:rdf=http://www.w3.org/1999/02/22-rdf-syntax-ns#
  xmlns:dc="http://purl.org/metadata/dublin_core#"
  xmlns:mydc="http://www.w3c.it/metadata/DCaddendum#">
  <rdf:Description about="http://www.dlib.org">
    <dc:Title>
        D-Lib Program - Research in Digital Libraries
    </dc:Title>
    <dc:Description>
        The D-Lib program supports the community of people
          with research interests in digital libraries and 
          electronic publishing
    </dc:Description>
    <dc:Publisher>
          Corporation For National Research Initiatives
    </dc:Publisher>
    <dc:Date>1995-01-07</dc:Date>
    <dc:Subject>
      <rdf:Bag>
        <rdf:li>Research; statistical methods</rdf:li>
        <rdf:li>Education, research, related topics</rdf:li>
        <rdf:li>Library use Studies</rdf:li>
      </rdf:Bag>
    </dc:Subject>
    <dc:Type>World Wide Web Home Page</dc:Type>
    <dc:Format>text/html</dc:Format>
    <dc:Language>en</dc:Language>
    <mydc:Rating>
       Well known and often referenced site
    </mydc:Rating>
    <mydc:Originality>High</mydc:Originality>
  </rdf:Description>
</rdf:RDF>