Different ways of Redefining group in Xsd?

Team,

Can any one let me know the different ways redefining group in xsd.

I am trying to load CDISC schema, but when we are trying to open it on visual studio (tried with different version) crashing/restarting the visual studio. We able to figure out the issue was with redefining the schema group.

<xs:schematargetNamespace="http://www.cdisc.org/ns/odm/v1.3"elementFormDefault="qualified"attributeFormDefault="unqualified"xmlns="http://www.cdisc.org/ns/odm/v1.3"xmlns:xs="http://www.w3.org/2001/XMLSchema"xmlns:sdm="http://www.cdisc.org/ns/studydesign/v1.0">

 <xs:importnamespace="http://www.cdisc.org/ns/studydesign/v1.0"schemaLocation="sdm-ns.xsd"/>

 <xs:redefineschemaLocation="../cdisc-odm-1.3.1/ODM1-3-1.xsd">

   <xs:groupname="ProtocolElementExtension">

     <xs:sequence>

       <xs:groupref="ProtocolElementExtension"/>

       <xs:groupref="ProtocolElementContents"/>

     </xs:sequence>

   </xs:group>

   <xs:groupname="StudyEventDefElementExtension">

     <xs:sequence>

       <xs:groupref="StudyEventDefElementExtension"/>

       <xs:groupref="StudyEventDefElementContents"/>

     </xs:sequence>

   </xs:group>

 </xs:redefine>

 <xs:groupname="ProtocolElementContents">

   <xs:sequence>

     <xs:elementref="sdm:Summary"minOccurs="0"maxOccurs="1"/>

     <xs:elementref="sdm:InclusionExclusionCriteria"minOccurs="0"maxOccurs="1"/>

     <xs:elementref="sdm:Structure"minOccurs="0"maxOccurs="1"/>

     <xs:elementref="sdm:Workflow"minOccurs="0"maxOccurs="1"/>

     <xs:elementref="sdm:Timing"minOccurs="0"maxOccurs="1"/>

   </xs:sequence>

 </xs:group>

 <xs:groupname="StudyEventDefElementContents">

   <xs:sequence>

     <xs:element ref="sdm:ActivityRef" minOccurs="0" maxOccurs="unbounded"/>

   </xs:sequence>

 </xs:group>

</xs:schema>

Can any one let me know the other option for redefinnig the structure