XACML Request with multiple subjects of the same attributeID?

<Request xmlns="urn:oasis:names:tc:xacml:2.0:context:schema:os" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <Subject>
    <Attribute AttributeId="urn:oasis:names:tc:xacml:1.0:subject:subject-id" DataType="http://www.w3.org/2001/XMLSchema#string">
      <AttributeValue>michael</AttributeValue>
    </Attribute>
    <Attribute AttributeId="group" DataType="http://www.w3.org/2001/XMLSchema#string">
      <AttributeValue>users</AttributeValue>
    </Attribute>
    <Attribute AttributeId="group" DataType="http://www.w3.org/2001/XMLSchema#string">
      <AttributeValue>administrators</AttributeValue>
    </Attribute>
    <Attribute AttributeId="group" DataType="http://www.w3.org/2001/XMLSchema#string">
      <AttributeValue>backupOperators</AttributeValue>
    </Attribute>
  </Subject>
  <Resource>
    <Attribute AttributeId="urn:oasis:names:tc:xacml:1.0:resource:resource-id" DataType="http://www.w3.org/2001/XMLSchema#string">
      <AttributeValue>/service/Address/URI</AttributeValue>
    </Attribute>
  </Resource>
  <Action>
    <Attribute AttributeId="urn:oasis:names:tc:xacml:1.0:action:action-id" DataType="http://www.w3.org/2001/XMLSchema#string">
      <AttributeValue>read</AttributeValue>
    </Attribute>
  </Action>
  <Environment/>
</Request>