The system schema can define attributes associated with the object types themselves – also known as meta-attributes. These attributes are rendered in a special ‘nav:objectTypeAttrs’ element in the object’s XML, e.g.:

  <audio nav:objectType="audio" id="obj44013" . . .>

    <nav:objectTypeAttrs mediaType="Audio" . . . />

    . . .

  </audio>

Use this element to write queries based on object type attributes, for example:

gn4:archiveObject[nav:objectTypeAttrs/@mediaType='Audio']

returns all the archive objects with a media type ‘Audio’, and

gn4:txt[nav:objectTypeAttrs/@typeKind='body']

returns all article’s text of kind ‘body’.