/** Prefix for facet query parameters */
    private static final String FACET_PREFIX = "facet.";

    /** Format identifier for PDF date parsing */
    private static final String PDF_DATE = "pdf_date";

    /** Regular expression pattern for matching email addresses */
    private static final Pattern EMAIL_ADDRESS_PATTERN =

    /** Mapping type for date fields. */
    public static final String MAPPING_TYPE_DATE = "date";

    /** Mapping type for PDF date fields. */
    public static final String MAPPING_TYPE_PDF_DATE = "pdf_date";

    // ============================================================
    // Request and Search Constants
    // ============================================================