skipping unmapped SAML 2.0 Attribute with Name

[Brian Reindel]

I've been reading up on the different reasons why this occurs, and I appear
to be following all the appropriate naming conventions. This is a custom
attribute name and it uses the
urn:oasis:names:tc:SAML:2.0:attrname-format:uri nameFormat.

attribute-resolver.xml:

<resolver:AttributeDefinition xsi:type="PrincipalName"
xmlns="urn:mace:shibboleth:2.0:resolver:ad" id="userPrincipalUsername">
    <resolver:AttributeEncoder xsi:type="SAML2String"
xmlns="urn:mace:shibboleth:2.0:attribute:encoder"
nameFormat="urn:oasis:names:tc:SAML:2.0:attrname-format:uri" name="
https://www.example.org/attributes/username" />
</resolver:AttributeDefinition>

Assertion:

...
<saml2:AttributeStatement>
    <saml2:Attribute
        Name="https://www.example.org/attributes/username"
NameFormat="urn:oasis:names:tc:SAML:2.0:attrname-format:uri">
        <saml2:AttributeValue
            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:type="xs:string">(my value is printed here)</saml2:AttributeValue>
    </saml2:Attribute>
</saml2:AttributeStatement>
...

attribute-map.xml

<Attribute name="https://www.example.org/attributes/username" id="username"
/>

I have also tried the following two formats, and neither work:

<Attribute name="urn:oasis:names:tc:SAML:2.0:attrname-format:uri:
https://www.example.org/attributes/username" id="username" />
<Attribute nameFormat="urn:oasis:names:tc:SAML:2.0:attrname-format:uri"
name="https://www.example.org/attributes/username" id="username" />

I always end up with the following INFO message and nothing in the request
for the service provider:

2013-07-19 16:58:53 INFO Shibboleth.AttributeExtractor.XML [5]: skipping
unmapped SAML 2.0 Attribute with Name:
https://www.example.org/attributes/username
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