function theme_rdf_metadata

Returns HTML for a series of empty spans for exporting RDF metadata in RDFa.

Sometimes it is useful to export data which is not semantically present in the HTML output. For example, a hierarchy of comments is visible for a human but not for machines because this hiearchy is not present in the DOM tree. We can express it in RDFa via empty <span> tags. These aren't visible and give machines extra information about the content and its structure.


$variables: An associative array containing:

  • metadata: An array of attribute arrays. Each item in the array corresponds to its own set of attributes, and therefore, needs its own element.

See also


Related topics

2 theme calls to theme_rdf_metadata()
rdf_preprocess_node in drupal/modules/rdf/rdf.module
Implements MODULE_preprocess_HOOK().
rdf_process in drupal/modules/rdf/rdf.module
Template process function for adding extra tags to hold RDFa attributes.


drupal/modules/rdf/rdf.module, line 858
Enables semantically enriched output for Drupal sites in the form of RDFa.


function theme_rdf_metadata($variables) {
  $output = '';
  foreach ($variables['metadata'] as $attributes) {

    // Add a class so that developers viewing the HTML source can see why there
    // are empty <span> tags in the document.
    $attributes['class'][] = 'rdf-meta';
    $attributes['class'][] = 'element-hidden';

    // The XHTML+RDFa doctype allows either <span></span> or <span /> syntax to
    // be used, but for maximum browser compatibility, W3C recommends the
    // former when serving pages using the text/html media type, see
    $output .= '<span' . drupal_attributes($attributes) . '></span>';
  return $output;