How to find which attribute extensions an OpenId provider supports?

I have been looking at http://code.google.com/p/openid4java/wiki/SampleConsumer and it is hardcoded to work with type "fetch_request开发者_如何学Python". Does it matter which type one wants, is there a way to tell or can one just use Fetch requests.

Many OPs are now advertising which extensions they support in their XRDS files. DotNetOpenAuth for example automatically uses sreg or AX depending on what the OP claims support for and this works in practive very well.

I am not familiar with openi4java though, so I can't say how easily you'll be able to do that for that library.

It seems that there is no definitive way to predict or request prior to a request what format the attributes will be returned. Therefore one must test all the various extension attribute types.