nucleus/deployment/schemas/src/main/resources/lib/schemas/xml.xsd

<?xml version='1.0'?>
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<!DOCTYPE xs:schema PUBLIC "-//W3C//DTD XMLSCHEMA 200102//EN" "XMLSchema.dtd" >
<xs:schema targetNamespace="http://www.w3.org/XML/1998/namespace" xmlns:xs="http://www.w3.org/2001/XMLSchema" xml:lang="en">

 <xs:annotation>
  <xs:documentation>
   See http://www.w3.org/XML/1998/namespace.html and
   http://www.w3.org/TR/REC-xml for information about this namespace.
  </xs:documentation>
 </xs:annotation>

 <xs:annotation>
  <xs:documentation>This schema defines attributes and an attribute group
        suitable for use by
        schemas wishing to allow xml:base, xml:lang or xml:space attributes
        on elements they define.

        To enable this, such a schema must import this schema
        for the XML namespace, e.g. as follows:
        &lt;schema . . .>
         . . .
         &lt;import namespace="http://www.w3.org/XML/1998/namespace"
                    schemaLocation="http://www.w3.org/2001/03/xml.xsd"/>

        Subsequently, qualified reference to any of the attributes
        or the group defined below will have the desired effect, e.g.

        &lt;type . . .>
         . . .
         &lt;attributeGroup ref="xml:specialAttrs"/>
 
         will define a type which will schema-validate an instance
         element with any of those attributes</xs:documentation>
 </xs:annotation>

 <xs:annotation>
  <xs:documentation>In keeping with the XML Schema WG's standard versioning
   policy, this schema document will persist at
   http://www.w3.org/2001/03/xml.xsd.
   At the date of issue it can also be found at
   http://www.w3.org/2001/xml.xsd.
   The schema document at that URI may however change in the future,
   in order to remain compatible with the latest version of XML Schema
   itself.  In other words, if the XML Schema namespace changes, the version
   of this document at
   http://www.w3.org/2001/xml.xsd will change
   accordingly; the version at
   http://www.w3.org/2001/03/xml.xsd will not change.
  </xs:documentation>
 </xs:annotation>

 <xs:attribute name="lang" type="xs:language">
  <xs:annotation>
   <xs:documentation>In due course, we should install the relevant ISO 2- and 3-letter
         codes as the enumerated possible values . . .</xs:documentation>
  </xs:annotation>
 </xs:attribute>

 <xs:attribute name="space" default="preserve">
  <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:annotation>
   <xs:documentation>See http://www.w3.org/TR/xmlbase/ for
                     information about this attribute.</xs:documentation>
  </xs:annotation>
 </xs:attribute>

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

</xs:schema>