public enum EXPathError {

    /** XPath static error 0001. */
    XPST0001("err:XPST0001:  Some component of the static context has not " + "been assigned a value."),

    /** XPath dynamic error 0004. */
    XPDY0002("err:XPDY0002:   Some part of the dynamic context has not " + "been assigned a value."),

    /** XPath static error 0003. */
    XPST0003("err:XPST0003: Expression is not a valid instance of the grammar" + "defined in A.1 EBNF."),

    /** XPath type error 0004. */
    XPTY0004("err:XPTY0004 The type is not appropriate the expression or the "
        + "typedoes not match a required type as specified by the matching rules."),

    /** XPath static error 0005. */
    XPST0005("err:XPST0005:  The static type assigned to an expression other than the "
        + "expression() or data(()) is empty-sequence()."),

    /** XPath static error 0008. */
    XPST0008("err:XPST0008 Expression refers to a name that is not defined in the " + "static context"),

    /** XPath static error 0010. */
    XPST0010("err:XPST0010: " + "Axis is not supported."),

    /** XPath static error 0017. */
    XPST0017("err:XPST0017  The expanded QName and number of arguments in a "
        + "function call do not match the name and arity of a function " + "signature."),

    /** XPath type error 0018. */
    XPTY0018("err:XPTY0018  Result of the last step "
        + "in a path expression contains both nodes and atomic values."),

    /** XPath type error 0019. */
    XPTY0019("err:XPTY0019  Result of a step (other "
        + "than the last step) in a path expression contains an atomic value."),

    /** XPath type error 0020. */
    XPTY0020("err:XPTY0020 Context item in an axis step is not a node."),

    /** XPath dynamic error 0050. */
    XPDY0050("err:XPDY0050 " + "Dynamic type of the operand of a treat expression does not match"
        + " the sequence type specified by the treat expression."),

    /** XPath static error 0051. */
    XPST0051("err:XPST0051 " + "Type is not defined in the in-scope schema types as an " + "atomic type."),

    /** XPath static error 0080. */
    XPST0080("err:XPST0080 " + "Target type of a cast or castable expression must not be "
        + "xs:NOTATION or xs:anyAtomicType."),

    /** XPath static error 0081. */
    XPST0081("err:XPST0081 " + "Namespace prefix cannot be expanded into a namespace URI by "
        + "using the statically known namespaces."),

    FOCA0001("err:FOCA0001, Input value too large for decimal."), FOCA0002(
        "err:FOCA0002, Invalid lexical value."),
        FOCA0003("err:FOCA0003, Input value too large for integer."), FOCA0005(
            "err:FOCA0005, NaN supplied as float/double value."), FOCA0006(
            "err:FOCA0006, String to be cast to decimal has too many digits of precision."), FOCH0001(
            "err:FOCH0001, Code point not valid."), FOCH0002("err:FOCH0002, Unsupported collation."),
        FOCH0003("err:FOCH0003, Unsupported normalization form."), FORH0004(
            "err:FOCH0004, Collation does not support collation units."), FODC0001(
            "err:FODC0001, No context document."), FODC0002("err:FODC0002, Error retrieving resource."),
        FODC0003("err:FODC0003, Function stability not defined."), FODC0004(
            "err:FODC0004, Invalid argument to fn:collection."), FODC0005(
            "err:FODC0005, Invalid argument to fn:doc or fn:doc-available."), FODT0001(
            "err:FODT0001, Overflow/underflow in date/time operation."), FODT0002(
            "err:FODT0002, Overflow/underflow in duration operation."), FODT0003(
            "err:FODT0003, Invalid timezone value."),
        FONS0004("err:FONS0004, No namespace found for prefix."), FONS0005(
            "err:FONS0005, Base-uri not defined in the static context."),
        /**
         * XQuery and XPath Function and Operators error 0001. This error is raised
         * whenever an attempt is made to divide by zero.
         */
        FOAR0001("err:FOAR0001: Division by zero."),
        /**
         * XQuery and XPath Function and Operators error 0002. This error is raised
         * whenever numeric operations result in an overflow or underflow.
         */
        FOAR0002("err:FOAR0002: Numeric operation overflow/underflow."), FOER0000(
            "err:FOER0000: Unidentified error."), FORG0001(
            "err:FORG0001, Invalid value for cast/constructor."), FORG0002(
            "err:FORG0002, Invalid argument to fn:resolve-uri()."), FORG0003(
            "err:FORG0003, fn:zero-or-one called with a sequence containing more than one item."), FORG0004(
            "err:FORG0004, fn:one-or-more called with a sequence containing no items."), FORG0005(
            "err:FORG0005, fn:exactly-one called with a sequence containing zero or more than one item."),
        /** XQuery and XPath Function and Operators error 0006. */
        FORG0006("err:FORG0006 Invalid argument type."), FORG0007(""), FORG0008(
            "err:FORG0008, Both arguments to fn:dateTime have a specified timezone."), FORG0009(
            "err:FORG0009, Error in resolving a relative URI against a base URI in fn:resolve-uri."),
        FORX0001("err:FORX0001, Invalid regular expression. flags"), FORX0002(
            "err:FORX0002, Invalid regular expression."), FORX0003(
            "err:FORX0003, Regular expression matches zero-length string."), FORX0004(
            "err:FORX0004, Invalid replacement string."), FOTY0012(
            "err:FOTY0012, Argument node does not have a typed value."), ;

    /** error message. */
    private final String mMessage;

        case YEAR_MONTH_DURATION:
        case DAY_TIME_DURATION:
            throw new IllegalStateException("Add operator is not implemented for the type "
                + returnType.getStringRepr() + " yet.");
        default:
            throw new XPathError(ErrorType.XPTY0004);

        }

        return new AtomicValue(value, typeKey);

    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected Type getReturnType(final int mOp1, final int mOp2) throws TTXPathException {

        Type type1;
        Type type2;
        try {
            type1 = Type.getType(mOp1).getPrimitiveBaseType();
            type2 = Type.getType(mOp2).getPrimitiveBaseType();
        } catch (final IllegalStateException e) {
            throw new XPathError(ErrorType.XPTY0004);
        }

        if (type1.isNumericType() && type2.isNumericType()) {

            // if both have the same numeric type, return it
            if (type1 == type2) {
                return type1;
            }

            if (type1 == Type.DOUBLE || type2 == Type.DOUBLE) {
                return Type.DOUBLE;
            } else if (type1 == Type.FLOAT || type2 == Type.FLOAT) {
                return Type.FLOAT;
            } else {
                assert (type1 == Type.DECIMAL || type2 == Type.DECIMAL);
                return Type.DECIMAL;
            }

        } else {

            switch (type1) {

            case YEAR_MONTH_DURATION:

    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected Type getReturnType(final int mOp1, final int mOp2) throws TTXPathException {

        Type type1;
        Type type2;
        try {
            type1 = Type.getType(mOp1).getPrimitiveBaseType();
            type2 = Type.getType(mOp2).getPrimitiveBaseType();
        } catch (final IllegalStateException e) {
            throw new XPathError(ErrorType.XPTY0004);
        }

        if (type1.isNumericType() && type2.isNumericType()) {

            // if both have the same numeric type, return it
            if (type1 == type2) {
                return type1;
            }

            if (type1 == Type.DOUBLE || type2 == Type.DOUBLE) {
                return Type.DOUBLE;
            } else if (type1 == Type.FLOAT || type2 == Type.FLOAT) {
                return Type.FLOAT;
            } else {
                assert (type1 == Type.DECIMAL || type2 == Type.DECIMAL);
                return Type.DECIMAL;
            }

        } else {

            switch (type1) {

            case YEAR_MONTH_DURATION:
                if (type2 == Type.YEAR_MONTH_DURATION) {

    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected Type getReturnType(final int mOp1, final int mOp2) throws TTXPathException {

        Type type1;
        Type type2;
        try {
            type1 = Type.getType(mOp1).getPrimitiveBaseType();
            type2 = Type.getType(mOp2).getPrimitiveBaseType();
        } catch (final IllegalStateException e) {
            throw new XPathError(ErrorType.XPTY0004);
        }

        if (type1.isNumericType() && type2.isNumericType()) {

            // if both have the same numeric type, return it
            if (type1 == type2) {
                return type1;
            }

            if (type1 == Type.DOUBLE || type2 == Type.DOUBLE) {
                return Type.DOUBLE;
            } else if (type1 == Type.FLOAT || type2 == Type.FLOAT) {
                return Type.FLOAT;
            } else {
                assert (type1 == Type.DECIMAL || type2 == Type.DECIMAL);
                return Type.DECIMAL;
            }

        } else {

            switch (type1) {

            case YEAR_MONTH_DURATION: