5.1 http://schemas.microsoft.com/office/excel/2006/main Schema

 <xsd:schema xmlns="http://schemas.microsoft.com/office/excel/2006/main" elementFormDefault="qualified" targetNamespace="http://schemas.microsoft.com/office/excel/2006/main" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:x="http://schemas.openxmlformats.org/spreadsheetml/2006/main">
   <xsd:import namespace="http://schemas.openxmlformats.org/spreadsheetml/2006/main" schemaLocation="xlbasictypes.xsd"/>
   <xsd:simpleType name="ST_Ref">
     <xsd:restriction base="xsd:string"/>
   </xsd:simpleType>
   <xsd:complexType name="CT_Ref">
     <xsd:simpleContent>
       <xsd:extension base="ST_Ref">
         <xsd:attribute name="edited" type="xsd:boolean" use="optional"/>
         <xsd:attribute name="adjusted" type="xsd:boolean" use="optional"/>
         <xsd:attribute name="adjust" type="xsd:boolean" use="optional"/>
       </xsd:extension>
     </xsd:simpleContent>
   </xsd:complexType>
   <xsd:simpleType name="ST_Sqref">
     <xsd:list itemType="ST_Ref"/>
   </xsd:simpleType>
   <xsd:complexType name="CT_Sqref">
     <xsd:simpleContent>
       <xsd:extension base="ST_Sqref">
         <xsd:attribute name="edited" type="xsd:boolean" use="optional"/>
         <xsd:attribute name="split" type="xsd:boolean" use="optional"/>
         <xsd:attribute name="adjusted" type="xsd:boolean" use="optional"/>
         <xsd:attribute name="adjust" type="xsd:boolean" use="optional"/>
       </xsd:extension>
     </xsd:simpleContent>
   </xsd:complexType>
   <xsd:element name="f" type="x:ST_Formula"/>
   <xsd:element name="ref" type="CT_Ref"/>
   <xsd:element name="sqref" type="CT_Sqref"/>
 </xsd:schema>