Does Daffodil support "failureType"?

[Roger L Costello]

I want to try out the failureType attribute that Mike mentioned the other day. 
The DFDL specification says that failureType is an attribute of xs:assert.

I have this in my DFDL schema:

<xs:element name="label">
    <xs:simpleType>
        <xs:annotation>
            <xs:appinfo source=http://www.ogf.org/dfdl/>
                <dfdl:assert testKind="expression"
                                   test="{dfdl:checkConstraints(.)}"
                                   message="Invalid label"
                                   failureType="recoverableError"/>
            </xs:appinfo>
        </xs:annotation>
        <xs:restriction base="xs:string">
            <xs:enumeration value="Dear Sir"/>
            <xs:enumeration value="Dear Madam"/>
        </xs:restriction>
    </xs:simpleType>
</xs:element>

When I run my DFDL schema I get this error message:

Attribute 'failureType' is not allowed to appear in element 'dfdl:assert'.

I looked at the schema for DFDL schemas and I don't see failureType declared 
anywhere.

I looked on the web page that lists the things that Daffodil does not currently 
support, and failureType is not listed there.

What's up with failureType? Does Daffodil support it?