unattend.xsd / autounattend.xsd taken from Windows ADK as per https://schneegans.de/windows/unattend-schema/

unattend.xsd

<?xml version="1.0" encoding="ASCII"?>
<xsd:schema targetNamespace="urn:schemas-microsoft-com:unattend" xmlns="urn:schemas-microsoft-com:unattend"
   xmlns:xsd="http://www.w3.org/2001/XMLSchema"
   elementFormDefault="qualified" attributeFormDefault="unqualified">

   <!--Root Elements-->
   <xsd:element name="unattend">
      <xsd:annotation>
         <xsd:documentation>Unattend</xsd:documentation>
      </xsd:annotation>
      <xsd:complexType>
         <xsd:complexContent>
            <xsd:extension base="unattendType" />
         </xsd:complexContent>
      </xsd:complexType>
   </xsd:element>

   <xsd:complexType name="unattendType">
      <xsd:sequence>
         <xsd:element name="servicing" type="servicingType" minOccurs="0" maxOccurs="1" />
         <xsd:element name="settings" type="settingType" minOccurs="0" maxOccurs="unbounded" />
         <xsd:any namespace="##other" processContents="lax" minOccurs="0" maxOccurs="unbounded" />
      </xsd:sequence>
      <xsd:attribute name="author" type="xsd:string" use="optional" />
      <xsd:attribute name="description" type="xsd:string" use="optional" />
      <xsd:attribute name="creationTimeStamp" type="xsd:dateTime" use="optional" />
      <xsd:attribute name="lastUpdateTimeStamp" type="xsd:dateTime" use="optional" />
      <xsd:attribute name="ConfigurationSetTimeStamp" type="xsd:dateTime" use="optional" />
      <xsd:anyAttribute namespace="##other" processContents="lax" />
   </xsd:complexType>

   <xsd:complexType name="servicingType">
      <xsd:sequence>
         <xsd:element name="package" type="packageType" minOccurs="0" maxOccurs="unbounded" />
      </xsd:sequence>
   </xsd:complexType>

   <xsd:complexType name="settingType">
      <xsd:sequence>
         <xsd:element name="component" type="componentSettingType" minOccurs="0" maxOccurs="unbounded" />
      </xsd:sequence>
      <xsd:attribute name="pass" type="passType" use="required" />
   </xsd:complexType>

   <xsd:complexType name="componentSettingType">
      <xsd:sequence>
         <xsd:any namespace="##any" processContents="lax" minOccurs="0" maxOccurs="unbounded" />
      </xsd:sequence>
      <xsd:attribute name="name" type="xsd:string" use="required" />
      <xsd:attribute name="version" type="fourPartVersionType" use="optional" />
      <xsd:attribute name="processorArchitecture" type="processorArchitectureType" use="required" />
      <xsd:attribute name="publicKeyToken" type="publicKeyTokenType" use="required" />
      <xsd:attribute name="language" type="xsd:string" use="required" />
      <xsd:attribute name="versionScope" type="versionScopeType" use="optional" default="nonSxS" />
   </xsd:complexType>

   <xsd:simpleType name="passType">
      <xsd:annotation>
         <xsd:documentation>Installation phase to perform setting</xsd:documentation>
      </xsd:annotation>
      <xsd:restriction base="xsd:string">
         <xsd:enumeration value="offlineServicing" />
         <xsd:enumeration value="windowsPE" />
         <xsd:enumeration value="generalize" />
         <xsd:enumeration value="specialize" />
         <xsd:enumeration value="auditSystem" />
         <xsd:enumeration value="auditUser" />
         <xsd:enumeration value="oobeSystem" />
         <xsd:enumeration value="oobeUser" />
      </xsd:restriction>
   </xsd:simpleType>

   <xsd:complexType name="packageType">
      <xsd:sequence>
         <xsd:element name="assemblyIdentity" type="identityType" />
         <xsd:choice minOccurs="0" maxOccurs="unbounded">
            <xsd:element name="source" type="sourceType" />
            <xsd:element name="selection" type="selectionType" />
         </xsd:choice>
      </xsd:sequence>
      <xsd:attribute name="action" type="actionType" use="required" />
      <xsd:attribute name="permanence" type="permanenceType" use="optional" default="removable" />
      <xsd:anyAttribute namespace="##other" processContents="lax" />
   </xsd:complexType>

   <xsd:complexType name="sourceType">
      <xsd:annotation>
         <xsd:documentation>Package source specification.</xsd:documentation>
      </xsd:annotation>
      <xsd:attribute name="location" type="xsd:string" use="required">
         <xsd:annotation>
            <xsd:documentation>Path to source location for package to install.</xsd:documentation>
         </xsd:annotation>
      </xsd:attribute>
      <xsd:attribute name="permanence" type="permanenceType" use="optional" default="permanent" />
   </xsd:complexType>

   <xsd:complexType name="selectionType">
      <xsd:annotation>
         <xsd:documentation>Selection state override for nested child packages.</xsd:documentation>
      </xsd:annotation>
      <xsd:attribute name="name" type="xsd:string" use="required">
         <xsd:annotation>
            <xsd:documentation>Name of selectable update within child package.</xsd:documentation>
         </xsd:annotation>
      </xsd:attribute>
      <xsd:attribute name="state" type="xsd:boolean" use="required">
         <xsd:annotation>
            <xsd:documentation>Boolean initial state for selection.</xsd:documentation>
         </xsd:annotation>
      </xsd:attribute>
   </xsd:complexType>

   <xsd:simpleType name="actionType">
      <xsd:annotation>
         <xsd:documentation>Installation action to perform on package.</xsd:documentation>
      </xsd:annotation>
      <xsd:restriction base="xsd:string">
         <xsd:enumeration value="remove" />      <!-- remove package from system -->
         <xsd:enumeration value="stage" />       <!-- fully stage package, ready for installation -->
         <xsd:enumeration value="install" />     <!-- install package on system, then configure -->
         <xsd:enumeration value="configure" />   <!-- configure currently installed package -->
      </xsd:restriction>
   </xsd:simpleType>

   <xsd:simpleType name="permanenceType">
      <xsd:annotation>
         <xsd:documentation>Uninstall options.</xsd:documentation>
      </xsd:annotation>
      <xsd:restriction base="xsd:string">
         <xsd:enumeration value="removable" />   <!-- normal uninstall behavior -->
         <xsd:enumeration value="permanent" />   <!-- cannot be removed -->
         <xsd:enumeration value="temporary" />   <!-- removed when any component updated -->
      </xsd:restriction>
   </xsd:simpleType>

   <xsd:complexType name="identityType">
      <xsd:attribute name="name" type="xsd:string" use="required" />
      <xsd:attribute name="version" type="fourPartVersionType" use="required" />
      <xsd:attribute name="processorArchitecture" type="processorArchitectureType" use="required" />
      <xsd:attribute name="publicKeyToken" type="publicKeyTokenType" use="required" />
      <xsd:attribute name="language" type="xsd:string" use="required" />
      <xsd:attribute name="versionScope" type="xsd:string" use="optional" fixed="nonSxS" />
   </xsd:complexType>

   <xsd:simpleType name="versionScopeType">
      <xsd:restriction base="xsd:string">
         <xsd:pattern value="((N|n)(E|e)(U|u)(T|t)(R|r)(A|a)(L|l))|((N|n)(O|o)(N|n)(S|s)(X|x)(S|s))" />
      </xsd:restriction>
   </xsd:simpleType>

   <xsd:simpleType name="fourPartVersionType">
      <xsd:restriction base="xsd:string">
         <xsd:pattern value="(0*[0-9]{0,4}|0*[1-5][0-9]{4}|0*6[0-4][0-9]{3}|0*65[0-4][0-9]{2}|0*655[0-2][0-9]|0*6553[0-5])\.(0*[0-9]{0,4}|0*[1-5][0-9]{4}|0*6[0-4][0-9]{3}|0*65[0-4][0-9]{2}|0*655[0-2][0-9]|0*6553[0-5])\.(0*[0-9]{0,4}|0*[1-5][0-9]{4}|0*6[0-4][0-9]{3}|0*65[0-4][0-9]{2}|0*655[0-2][0-9]|0*6553[0-5])\.(0*[0-9]{0,4}|0*[1-5][0-9]{4}|0*6[0-4][0-9]{3}|0*65[0-4][0-9]{2}|0*655[0-2][0-9]|0*6553[0-5])$" />
      </xsd:restriction>
   </xsd:simpleType>

   <xsd:simpleType name="publicKeyTokenType">
      <xsd:restriction base="xsd:string">
         <xsd:pattern value="([0-9]|[a-f]|[A-F]){16}" />
      </xsd:restriction>
   </xsd:simpleType>

   <xsd:simpleType name="processorArchitectureType">
      <xsd:restriction base="xsd:string">
         <xsd:pattern value="((X|x)86)|((I|i)(A|a)64)|((A|a)(M|m)(D|d)64)|((W|w)(O|o)(W|w)64)|((M|m)(S|s)(I|i)(L|l))|((S|s)(H|h)(X|x))|((A|a)(R|r)(M|m))|((D|d)(A|a)(T|t)(A|a))|((N|n)(E|e)(U|u)(T|t)(R|r)(A|a)(L|l))" />
      </xsd:restriction>
   </xsd:simpleType>

</xsd:schema>