xml.xsd

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema targetNamespace="http://www.w3.org/XML/1998/namespace"
    xmlns:xs="http://www.w3.org/2001/XMLSchema" xml:lang="en">

    <xs:attribute name="lang">
        <xs:simpleType>
            <xs:union memberTypes="xs:language">
                <xs:simpleType>
                    <xs:restriction base="xs:string">
                        <xs:enumeration value="" />
                    </xs:restriction>
                </xs:simpleType>
            </xs:union>
        </xs:simpleType>
    </xs:attribute>

    <xs:attribute name="space">
        <xs:simpleType>
            <xs:restriction base="xs:NCName">
                <xs:enumeration value="default" />
                <xs:enumeration value="preserve" />
            </xs:restriction>
        </xs:simpleType>
    </xs:attribute>

    <xs:attribute name="base" type="xs:anyURI">
    </xs:attribute>

    <xs:attribute name="id" type="xs:ID">
    </xs:attribute>

    <xs:attributeGroup name="specialAttrs">
        <xs:attribute ref="xml:base" />
        <xs:attribute ref="xml:lang" />
        <xs:attribute ref="xml:space" />
        <xs:attribute ref="xml:id" />
    </xs:attributeGroup>
</xs:schema>