Use of non-schema namespaced attributes on appinfo

I have an application-specific attribute that I need to store on a  
schema component.  The XMLSchema spec states that non-schema  
namespaced attributes are allowed on the <appinfo> tag, but several  
books on the subject suggest that this isn’t the case.

So, for the case where I want to store foo:myAttr on a schema  
component, should I use:

    <xs:annotation>
       <xs:appinfo xmlns:foo=”http://whatever” foo:myAttr=”someValue”/>
    </xs:annotation>

or the more verbose:

    <xs:annotation>
       <xs:appinfo>
          <foo:myHolder xmlns:foo=”http://whatever” myAttr=”someValue”/>
       </xs:appinfo>
    </xs:annotation>

I prefer the former (which doesn’t require the somewhat artificial  
construction of a holder element), but I’d rather do the latter if it  
represents the intended (or universally practiced) usage.

Thanks,
-- Jeff Young
Adobe Systems, Inc