title: RDF - citations for predicates
body: <p>I'm attempting to create/implement an RDF-schema for historical data: setting up a base schema is simple, but I've run into a roadblock when trying to add a verifiable source for each claim (predicate).</p>
  
  <p>For example, it's relatively easy to declare 'Alexander (subject) has a brother (predicate) Robert (object)'... but I would like that claim (that is the whole) that Robert was indeed Alexander's brother to be cited, with a link to the original source document, if possible.</p>
  
  <p>The best I could come up with is a 'doubled triplet' schema:</p>
  
  <pre><code>    Alexander -&gt; has_a_brother -&gt; Robert
      Alexander -&gt; has_a_brother_source -&gt; 'http://sourcedocumentserver.com/blablabla'
      Alexander -&gt; has_a_brother_source -&gt; 'http://sourcedocumentserver2.com/blablabla'
      Alexander -&gt; has_a_brother_source -&gt; 'http://sourcedocumentserver3.com/blablabla'
  </code></pre>
  
  <p>Is there a better way to go about this?</p>
  
  <p>PS: this problem is a bit different than a 'predicate variable' (like the question that this one was said to replicate), but in this 'citation needed' circumstance, <em>every single predicate in the database</em> would need a secondary description/label/name (and that's even without imagining multiple citations, attribution data, etc.).</p>
  
  <p>The best I could find was transforming every 'citation needed' predicate into a named graph (with multiple RDF triplets) that would contain the object normally directly joined (if no citation were required).</p>