+ * - indicates the type of relationship between returned sequences,
+ * xrf, and sequenceI that is required.
+ * <ul>
+ * <li>direct implies xrf is a primary reference for sequenceI AND
+ * the sequences to be located (eg a uniprot ID for a protein
+ * sequence, and a uniprot ref on a transcript sequence).</li>
+ * <li>indirect means xrf is a cross reference with respect to
+ * sequenceI or all the returned sequences (eg a genomic reference
+ * associated with a locus and one or more transcripts)</li>
+ * </ul>