code: @Override
  	public Structure getDomain(String pdpDomainName, AtomCache cache) throws IOException, StructureException {
  		return cache.getStructure(getPDPDomain(pdpDomainName));
  	}
docs: Get the structure for a particular PDP domain
  @param pdpDomainName PDP identifier, e.g. "PDP:4HHBAa"
  @param cache AtomCache, responsible for fetching and storing the coordinates
  @return Structure representing the PDP domain
  @throws IOException if the server cannot be reached
  @throws StructureException For errors parsing the structure