code: @Override
      public boolean documentExists(URI documentUri) throws DocumentException {
          URI fileUri = getDocumentInternalUri(documentUri);
          File file = new File(fileUri);
          return file.exists();
      }
docs: /* (non-Javadoc)
  @see uk.ac.open.kmi.iserve.sal.manager.DocumentManager#documentExists(java.net.URI)