@Override
  public Resource objectToJena(Model toAddTo, Protocol protocol) throws IllegalArgumentException {

    if (protocol.getResourceURL() == null) {
      throw new IllegalArgumentException(String.format(msg_ResourceWithoutURI, "protocols"));
    }
    Resource res = toAddTo.createResource(protocol.getResourceURL().toString());
    toAddTo.add(res, RDF.type, TOXBANK.PROTOCOL);

    if (protocol.isSearchable() != null)
      res.addLiteral(TOXBANK.ISSUMMARYSEARCHABLE, protocol.isSearchable());

    res.addLiteral(TOXBANK.HASVERSIONINFO, protocol.getVersion());

    if (protocol.getTitle() != null) res.addLiteral(DCTerms.title, protocol.getTitle());

    if (protocol.getTimeModified() != null)
      res.addLiteral(DCTerms.modified, protocol.getTimeModified());

    if (protocol.getSubmissionDate() != null)
      res.addLiteral(DCTerms.dateSubmitted, protocol.getSubmissionDate());

    if (protocol.isPublished() != null) res.addLiteral(TOXBANK.ISPUBLISHED, protocol.isPublished());

    if (protocol.getStatus() != null)
      res.addLiteral(TOXBANK.HASSTATUS, protocol.getStatus().name());

    if (protocol.getIdentifier() != null)
      res.addLiteral(DCTerms.identifier, protocol.getIdentifier());

    if (protocol.getAbstract() != null)
      res.addLiteral(TOXBANK.HASABSTRACT, cleanLiteral(protocol.getAbstract()));

    List<String> keywords = protocol.getKeywords();
    if (keywords != null) {
      for (String keyword : keywords) res.addLiteral(TOXBANK.HASKEYWORD, keyword);
    }

    if (protocol.getProjects() != null)
      for (Project aproject : protocol.getProjects()) {
        if (aproject.getResourceURL() == null)
          throw new IllegalArgumentException(
              String.format(msg_InvalidURI, "project", res.getURI()));
        Resource project = projectIO.objectToJena(toAddTo, aproject);
        res.addProperty(TOXBANK.HASPROJECT, project);
      }

    if (protocol.getOrganisation() != null) {
      if (protocol.getOrganisation().getResourceURL() == null)
        throw new IllegalArgumentException(
            String.format(msg_InvalidURI, "organisation", res.getURI()));
      Resource org = organisationIO.objectToJena(toAddTo, protocol.getOrganisation());
      res.addProperty(TOXBANK.HASORGANISATION, org);
    }

    if (protocol.getOwner() != null) {
      if (protocol.getOwner().getResourceURL() == null)
        throw new IllegalArgumentException(
            String.format(msg_InvalidURI, "protocol owner", res.getURI()));

      Resource ownerRes = toAddTo.createResource(protocol.getOwner().getResourceURL().toString());
      res.addProperty(TOXBANK.HASOWNER, ownerRes);
    }
    ToxBankResourceSet<User> authors = protocol.getAuthors();
    if (authors != null)
      for (User author : authors) {
        if (author.getResourceURL() == null)
          throw new IllegalArgumentException(String.format(msg_InvalidURI, "author", res.getURI()));
        Resource user = userIO.objectToJena(toAddTo, author);
        res.addProperty(TOXBANK.HASAUTHOR, user);
      }

    if (protocol.getDocument() != null) {
      if (protocol.getDocument().getResourceURL() == null)
        throw new IllegalArgumentException(String.format(msg_InvalidURI, "document", res.getURI()));

      Resource documentRes =
          toAddTo.createResource(protocol.getDocument().getResourceURL().toString());
      res.addProperty(TOXBANK.HASDOCUMENT, documentRes);
    }

    if (protocol.getDataTemplate() != null) {
      if (protocol.getDataTemplate().getResourceURL() == null)
        throw new IllegalArgumentException(
            String.format(msg_InvalidURI, "data template", res.getURI()));

      Resource templateRes =
          toAddTo.createResource(protocol.getDataTemplate().getResourceURL().toString());
      res.addProperty(TOXBANK.HASTEMPLATE, templateRes);
    }
    if (protocol.getLicense() != null) {
      toAddTo.add(res, DCTerms.license, toAddTo.createResource(protocol.getLicense().toString()));
    }

    return res;
  }