I registered for a web app last week. It imported most of my profile from OpenID simple registration. But I want an avatar. If you’ve used myspace, then you get the idea of a profile picture. If you’ve posted on a site supporting gravatars, you know how nifty it is to get that little picture next to your post. I want this nifty feature as a yadis (nee xrds-simple) service with my OpenId. That means we have to invent something.

Here goes:

<Service priority="30">
  <Type>http://josephholsten.com/avatar/1.0</Type>
  <URI>http://en.gravatar.com/userimage/529392/71f60655008051cefc0474c09dac3289</URI>
</Service>

What is it? A yadis document specifying my avatar URI. Along with it might lie LID, OAuth, or OpenID service descriptions. The type element is just an example right now, I’ll be needing a real service descriptor URI before this is a standard. But the URI element is interesting. That’s my gravatar! Or rather, it’s a URL for a real live image somewhere on the internet. For the geeks out there, we should assume that the URL responds with the appropriate mime type. Even better, it should convert into the appropriate mime type that is requested of it, REST style. But if places like jyte like this, you won’t have to upload images to every OpenID supporting site out there, it’ll just figure it out.

I have considered that simple registration extensions might provide this role. The problem lies with updating information. I change my avatar often enough to reflect my current appearence. Simple Registration really should apply just to the one time act of registering at an OpenID relying party. This is not a one time sort of use case. Thus the new service type.

Some problems are unresolved. Gravatar, the gold standard for globally recognized avatars, supports multiple image sizes and filtering by appropriateness. This could be solved by having multiple services in your XRDS, with each service providing an optional size and appropriatness rating. Alternatively, the service URI could support HTTP GET parameters to specify those attributes. While both reasonable for Every Use Case, I feel that Usually, it is best left as the Relying Party’s problem. Or rather, You Aren’t Going To Need It.