/**
     * Default constructor.
     */
    protected SearchRequestParams() {
        // Default constructor
    }

    /** The parameter for negative query. */
    public static final String AS_NQ = "nq";

    /** The parameter for OR query. */
    public static final String AS_OQ = "oq";

    /** The parameter for exact phrase query. */
    public static final String AS_EPQ = "epq";