* The value is, e.g. fess_user <br>
     * comment: Index name for user data.
     * @return The value of found property. (NotNull: if not found, exception but basically no way)
     */
    String getIndexUserIndex();

    /**
     * Get the value for the key 'index.log.index'. <br>
     * The value is, e.g. fess_log <br>
     * comment: Index name for log data.