[OpenID] When a parameter is optional, can the key still be there?

[Andrew Arnott]

I noticed a behavior of an older OpenId library I'm trying to interop with, and wondered if its behavior was considered inline with the spec or not.  I think the spec is vague in this area...

It gives openid.trust_root on the querystring, but leaves the value empty.  trust_root is optional, but so far it seems everyone has interpreted that as "if you don't intend to include a value, don't include the key."  But this particular library does include the key and an empty string for a value.  Is this ok?  
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