http://www.openmeta.org/2000/PhotoRDF/content-1-0#
Copyright 2001 David Dodds
<rdf:RDF
    xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
    xmlns="http://www.w3.org/TR/1999/PR-rdf-schema#"
    xmlns:content="">
  <!-- "" is the same as 
"http://www.openmeta.org/2000/PhotoRDF/content-1-0#" -->
  <!-- "" modeled on  "http://www.w3.org/2000/PhotoRDF/content-1-0#" -->

  <Class rdf:ID="Keywords">
    <comment xml:lang="en">An enumeration of keywords to
      describe the subject of circuits.</comment>
  </Class>

  <content:Keywords rdf:ID="Circuit">
    <label xml:lang="en">Circuit</label>
  </content:Keywords>

  <content:Keywords rdf:ID="Resistor">
    <label xml:lang="en">Resistor</label>
  </content:Keywords>

  <content:Keywords rdf:ID="Capacitor">
    <label xml:lang="en">Capacitor</label>
  </content:Keywords>

  <content:Keywords rdf:ID="Inductor">
    <label xml:lang="en">Inductor</label>
  </content:Keywords>

  <content:Keywords rdf:ID="Variable Resistor">
    <label xml:lang="en">Variable Resistor</label>
  </content:Keywords>

  <content:Keywords rdf:ID="Variable Capacitor">
    <label xml:lang="en">Variable Capacitor</label>
  </content:Keywords>

  <content:Keywords rdf:ID="Battery">
    <label xml:lang="en">Battery</label>
  </content:Keywords>

  <content:Keywords rdf:ID="Antenna">
    <label xml:lang="en">Antenna</label>
  </content:Keywords>

  <content:Keywords rdf:ID="Transistor">
    <label xml:lang="en">Transistor</label>
  </content:Keywords>

  <content:Keywords rdf:ID="Diode">
    <label xml:lang="en">Diode</label>
  </content:Keywords>

  <content:Keywords rdf:ID="Varactor">
    <label xml:lang="en">Varactor</label>
  </content:Keywords>


    <content:Keywords rdf:ID="Tunnel Diode">
      <label xml:lang="en">Tunnel Diode</label>
  </content:Keywords>

    <content:Keywords rdf:ID="Thermistor">
      <label xml:lang="en">Thermistor</label>
  </content:Keywords>

    <content:Keywords rdf:ID="Photocell">
      <label xml:lang="en">Photocell</label>
  </content:Keywords>

    <content:Keywords rdf:ID="Cats Whisker Galena Crystal">
      <label xml:lang="en">Cats Whisker Galena Crystal</label>
  </content:Keywords>

    <content:Keywords rdf:ID="Light Emitting Diode">
      <label xml:lang="en">Light Emitting Diode</label>
  </content:Keywords>

    <content:Keywords rdf:ID="Smoke Emitting Diode">
      <label xml:lang="en">Smoke Emitting Diode</label>
  </content:Keywords>

</rdf:RDF>

Appendix B: example of metadata
This is an example of  metadata in RDF format that is generated.
<?xml version="1.0"?>
<rdf:RDF
     xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
     xmlns:DC="http://purl.oclc.org/dc/documents/rec-dces-199809.htm#"
     xmlns:Circuit="http://www.openmeta.org/2000/PhotoRDF/circuit-1-0#">
  <rdf:Description about="">
    <DC:Coverage>Circuit 25 revision 7</DC:Coverage>
    <DC:Source>Photo</DC:Source>
    <DC:Relation>Circuit 25</DC:Relation>
    <DC:Date>2000-04-01</DC:Date>
    <DC:Description>A schematic diagram of a GA circuit is 
shown.</DC:Description>
    <DC:Publisher rdf:resource="http://www.openmeta.org/People/David/"/>
    <DC:Title>Gravitic Anomalizer Circuit 25 Revision 7</DC:Title>
    <DC:Type>image</DC:Type>
    <DC:Format>image/jpeg</DC:Format>
    <DC:Identifier>000401</DC:Identifier>
    <DC:Creator rdf:resource="http://www.openmeta.org/People/David"/>
    <Circuit:inductor 
rdf:resource="http://www.openmeta.org/People/David/Circuit25v7"/>
    <Circuit:variableresistor 
rdf:resource="http://www.openmeta.org/People/David/Circuit25v7"/>
    <Circuit:capacitor 
rdf:resource="http://www.openmeta.org/People/David/Circuit25v7"/>
    <Circuit:battery 
rdf:resource="http://www.openmeta.org/People/David/Circuit25v7"/>
    <Circuit:antenna 
rdf:resource="http://www.openmeta.org/People/David/Circuit25v7"/>
  </rdf:Description>
  <rdf:Description about="battery">
  	  	 <daxsvg:AtRight resource="variableresistor"/>
	</rdf:Description>
  <rdf:Description about="battery">
	         <daxsvg:Touching resource="variableresistor"/>
	</rdf:Description>
  <rdf:Description about="variableresistor">
		 <daxsvg:AtRight resource="inductor"/>
	</rdf:Description>
  <rdf:Description about="variableresistor">
		  <daxsvg:Touching resource="inductor"/>
	</rdf:Description>
  <rdf:Description about="inductor">
		 <daxsvg:Touching resource="capacitor"/>
	</rdf:Description>
  <rdf:Description about="inductor">
		 <daxsvg:AtRight resource="capacitor"/>
	</rdf:Description>
  <rdf:Description about="capacitor">
		 <daxsvg:AtRight resource="antenna"/>
	</rdf:Description>
  <rdf:Description about="capacitor">
		 <daxsvg:Touching resource="antenna"/>
	</rdf:Description>
</rdf:RDF>