How make univoque my enumeration by xs:unique - xsd

Question

Can anyone point me as to why the unique element in my XSD is not forcing unique-ness? This should throw an error because the last ScreenResult element does not contain a unique value for the Type attribute. I should also note that I'm truly after forcing one of each Type within ScreenResults (ScreenResult is required to exist 3 times, there are 3 types of screens and I am requiring unique-ness) so if there is a better way to accomplish that, I'm all for that as well.
Thank you.
Here is my XML snippet:
<ScreenResults>
<ScreenResult Type="Screen Type A">1</ScreenResult>
<ScreenResult Type="Screen Type B">1</ScreenResult>
<ScreenResult Type="Screen Type B">2</ScreenResult>
</ScreenResults>
Here is my XSD snippet (also note that my original XSD snippets span multiple files but I have verified all of my namespaces are correct):
<xs:element name="ScreenResults" type="import:ScreenResults" minOccurs="0" maxOccurs="1">
<xs:unique name="UniqueScreenResults">
<xs:selector xpath="ScreenResult" />
<xs:field xpath="#Type" />
</xs:unique>
</xs:element>
<!--============ ScreenResults =============-->
<xs:complexType name="ScreenResults">
<xs:sequence minOccurs="1" maxOccurs="1">
<xs:element name="ScreenResult" minOccurs="3" maxOccurs="3">
<xs:complexType>
<xs:simpleContent>
<xs:extension base="enum:ScreenResult">
<xs:attribute name="Type" type="enum:ScreenType" use="required" />
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:element>
</xs:sequence>
</xs:complexType>
<!--============= ScreenType =============-->
<xs:simpleType name="ScreenType">
<xs:restriction base='xs:token'>
<xs:enumeration value='Screen Type A' >
<xs:annotation>
<xs:documentation>1</xs:documentation>
</xs:annotation>
</xs:enumeration>
<xs:enumeration value='Screen Type B' >
<xs:annotation>
<xs:documentation>2</xs:documentation>
</xs:annotation>
</xs:enumeration>
<xs:enumeration value='Screen Type C' >
<xs:annotation>
<xs:documentation>3</xs:documentation>
</xs:annotation>
</xs:enumeration>
</xs:restriction>
</xs:simpleType>
<!--============ ScreenResult ============-->
<xs:simpleType name="ScreenResult">
<xs:restriction base='xs:token'>
<xs:enumeration value='1' >
<xs:annotation>
<xs:documentation>Positive</xs:documentation>
</xs:annotation>
</xs:enumeration>
<xs:enumeration value='2' >
<xs:annotation>
<xs:documentation>Negative</xs:documentation>
</xs:annotation>
</xs:enumeration>
<xs:enumeration value='3' >
<xs:annotation>
<xs:documentation>Not administered</xs:documentation>
</xs:annotation>
</xs:enumeration>
</xs:restriction>
</xs:simpleType>

Answer 1

I'm posting my solution for anyone else who runs into this problem.
Although I had asserted that all of my namespaces were correct, that was, of course the problem. All of the namespaces were correct except on the unique element itself.
I erroneously assumed that the unique element would not need to prefix a namespace as it was within the context. But that is not the case. Since I did declare a default namespace for the file, I still needed the prefix.
So my only change, and the solution, is as follows:
<xs:element name="ScreenResults" type="import:ScreenResults" minOccurs="0" maxOccurs="1">
<xs:unique name="UniqueScreenResults">
<xs:selector xpath="import:ScreenResult" />
<xs:field xpath="#Type" />
</xs:unique>
</xs:element>