Adding namespace to single element doesn't conform to xsd

All I want to do is add a single namespace to a single element, S_NO, but I can't figure it out. Help would be appreciated. I keep getting errors when I add prefixes and stuff on the element. It won't recognise the element that is called within the XSD when using XMLSpy.

XML Code:

<MSG xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="file:///C:/test_xml/izzypod5/test_input.xsd">
 <BODY>
   <bar:S_NO xmlns:bar="http://www.bar.org/">4423</bar:S_NO>
 </BODY>
</MSG>

XSD Code:

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:bar="http://www.bar.org/">
<!-- Element Declarations -->
<xs:element name="S_NO" type="S_NOType" nillable="true">
    <xs:annotation>
        <xs:documentation>S_No; Mandatory Field</xs:documentation>
    </xs:annotation>
</xs:element>
<xs:element name="BODY" type="BODYType">
    <xs:annotation>
        <xs:documentation>Body</xs:documentation>
    </xs:annotation>
</xs:element>
<xs:element name="MSG" type="MSGType">
    <xs:annotation>
        <xs:documentation>Message encapsulates Body</xs:documentation>
    </xs:annotation>
</xs:element>
<xs:simpleType name="S_NOType">
    <xs:restriction base="xs:string">
        <xs:minLength value="0"/>
        <xs:maxLength value="15"/>
    </xs:restriction>
</xs:simpleType>
<!-- Complex Type Declarations -->
<xs:complexType name="BODYType">
    <xs:sequence>
        <xs:element ref="S_NO"/>
    </xs:sequence>
</xs:complexType>
<xs:complexType name="MSGType">
    <xs:sequence>
        <xs:element ref="BODY"/>
    </xs:sequence>
</xs:complexType>
<xs:complexType name="REQUEST_MSGType">
    <xs:sequence>
        <xs:element ref="MSG"/>
    </xs:sequence>
</xs:complexType>
</xs:schema>

Solution

You have to use another XSD for the element you wish to have in a different namespace.

XML document instance:

<?xml version="1.0" encoding="UTF-8"?>
<MSG xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:noNamespaceSchemaLocation="file:///C:/test_xml/izzypod5/test_input.xsd"
     xmlns:bar="http://www.bar.org/">
  <BODY>
    <bar:S_NO xmlns:bar="http://www.bar.org/">4423</bar:S_NO>
  </BODY>
</MSG>

Main XSD:

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
           xmlns:bar="http://www.bar.org/">

  <xs:import namespace="http://www.bar.org/" schemaLocation="bar.xsd"/>

  <!-- Element Declarations -->
  <xs:element name="BODY" type="BODYType">
    <xs:annotation>
      <xs:documentation>Body</xs:documentation>
    </xs:annotation>
  </xs:element>
  <xs:element name="MSG" type="MSGType">
    <xs:annotation>
      <xs:documentation>Message encapsulates Body</xs:documentation>
    </xs:annotation>
  </xs:element>
  <!-- Complex Type Declarations -->
  <xs:complexType name="BODYType">
    <xs:sequence>
      <xs:element ref="bar:S_NO"/>
    </xs:sequence>
  </xs:complexType>
  <xs:complexType name="MSGType">
    <xs:sequence>
      <xs:element ref="BODY"/>
    </xs:sequence>
  </xs:complexType>
  <xs:complexType name="REQUEST_MSGType">
    <xs:sequence>
      <xs:element ref="MSG"/>
    </xs:sequence>
  </xs:complexType>
</xs:schema>

Supporting XSD (bar.xsd) for S_NO:

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
           xmlns:bar="http://www.bar.org/"
           targetNamespace="http://www.bar.org/">
  <xs:element name="S_NO" type="bar:S_NOType" nillable="true">
    <xs:annotation>
      <xs:documentation>S_No; Mandatory Field</xs:documentation>
    </xs:annotation>
  </xs:element>
  <xs:simpleType name="S_NOType">
    <xs:restriction base="xs:string">
      <xs:minLength value="0"/>
      <xs:maxLength value="15"/>
    </xs:restriction>
  </xs:simpleType>
</xs:schema>