Different target namespace error

[em]

Hi,

I've been struggling to resolve this issue for a week now and haven't gotten
any responses on StackOverflow
(http://stackoverflow.com/questions/31971324/error-different-target-namespace-but-schema-validates-and-namespaces-match),
so I found this list.

I managed to reduce my original complex files down to shorter examples which
demonstrate the issue. I'm able to validate this XML:

<?xml version="1.0" encoding="UTF-8" standalone="no" ?>
<My_Data>
    <PartOne>
        testing
    </PartOne>
    <PartTwo>
        123
    </PartTwo>
</My_Data>

with this XSD:

<xs:schema
    xmlns:xs="http://www.w3.org/2001/XMLSchema";
    elementFormDefault="qualified">
    <xs:element name="My_Data">
        <xs:complexType>
            <xs:sequence>
                <xs:element name="PartOne" type="xs:string" minOccurs="0"
maxOccurs="1"/>
                <xs:element name="PartTwo" type="xs:integer" minOccurs="0"
maxOccurs="unbounded"/>
            </xs:sequence>
        </xs:complexType>
    </xs:element>
</xs:schema>

However, as soon as I add a targetNamespace attribute in the schema, I get
the error "has a different target namespace from the one specified in the
instance document ."

XML:

<?xml version="1.0" encoding="UTF-8" standalone="no" ?>
<My_Data
    xmlns="http://www.mywebsite.com/schema/myschema";
    xmlns:xsi="http://www.w3.org/2001/XMLSchema";>
    <PartOne>
        <ElemOne>thing</ElemOne>
    </PartOne>
    <PartTwo>123</PartTwo>
</My_Data>

XSD:

<xs:schema
        xmlns="http://www.mywebsite.com/schema/myschema";
        xmlns:xs="http://www.w3.org/2001/XMLSchema";
        elementFormDefault="qualified"
        attributeFormDefault="unqualified"
        targetNamespace="http://www.mywebsite.com/schema/myschema";>
    <xs:element name="My_Data">
        <xs:complexType>
            <xs:sequence>
                <xs:element name="PartOne" type="SubType" minOccurs="0"
maxOccurs="1"/>
                <xs:element name="PartTwo" type="xs:integer" minOccurs="0"
maxOccurs="unbounded"/>
            </xs:sequence>
        </xs:complexType>
    </xs:element>
    <xs:complexType name="SubType">
        <xs:sequence>
            <xs:element name="ElemOne" type="xs:string" />
        </xs:sequence>
    </xs:complexType>
</xs:schema>

But the XML and XSD validate! Why would this be? I've tried adding a
schemaLocation attribute and searched for other examples, but can't figure
out what is going on here.

Any insight would be greatly appreciated!

Thanks,

em