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Digital object relationship metadata is a way of asserting these various kinds of relationships for Fedora objects. A default set of common relationships is defined in the Fedora relationship ontology (actually, a simple RDF schema) which defines a set of common generic relationships useful in creating digital object networks. These relationships can be refined or extended. Also, communities can define their own ontologies to encode relationships among Fedora digital objects. Relationships are asserted from the perspective of one object to another object as in the following general pattern:panel

<subjectFedoraObject>    <relationshipProperty>    <targetFedoraObject>

The first Fedora object is considered the "subject" of the relationship assertion. The relationship, itself, is considered a property of the subject. The target Fedora object is the related object. Thus, a valid relationship assertion as an English-language sentence might be:panel

<MyCatVideo>    <is a member of the collection>    <GreatCatVideos>

Using RELS-INT, relationships can also be asserted from the datastream of one object to another object or datastream.

<MyCatPicture/Thumbnail>    <is thumbnail of>    <MyCatPicture/FullSizeImage>

Why are Fedora Digital Object Relationships Important?

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why why

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The syntax for asserting RELS-EXT relationships in RDF is as follows:

<rdf:RDF
  xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
  xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"
  xmlns:fedora="info:fedora/fedora-system:def/relations-external#"
  xmlns:myns="http://www.nsdl.org/ontologies/relationships#">
  <rdf:Description rdf:about="info:fedora/demo:99">
	<fedora:isMemberOfCollection rdf:resource="info:fedora/demo:c1"/>
	<myns:isPartOf rdf:resource="info:fedora/mystuff:100"/>
	<myns:owner>Jane Doe</myns:owner>
  </rdf:Description>
</rdf:RDF>

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The syntax for asserting RELS-INT relationships in RDF is as follows:

<rdf:RDF
  xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
  xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"
  xmlns:fedora="info:fedora/fedora-system:def/relations-external#"
  xmlns:myns="http://www.nsdl.org/ontologies/relationships#">
  <rdf:Description rdf:about="info:fedora/demo:99/Thumbnail">
	<myns:isThumbnailOf rdf:resource="info:fedora/demo:99/FullSizeImage"/>
  </rdf:Description>
  <rdf:Description rdf:about="info:fedora/demo:99/FullSizeImage">
	<myns:hasImageSize>1600 x 900</myns:hasImageSize>
  </rdf:Description>
</rdf:RDF>

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