Please add your use case here: a method of using Yadis to accomplish various tasks, for the purpose of illustrating the many uses for Yadis.
Within XML-VCards -- the version of VCards we use for profile data representation in LID -- there's an element called PHOTO. I've seen people use this to point to a photo of themselves.
To get at it from a Yadis environment, do this:
1) take identity URL
2) determine whether it supports the LID Traversal Profile and the LID VCard profile, and from which URL (let's call that the LIDURL)
3) perform HTTP GET on LIDURL?xpath=/VCARD/PHOTO
I have gone through the steps to add relying party capabilities to my Wiki. I want to now use that to determine who can access information from an RSS feed from that Wiki site.
A community web site requires all posters to be above 13 years old. While signing up, the user's page at the identity URL shows a request for an "age 13 or above" proof. It presents a list of compatible proofs the user has stored, or else a list of providers who the community is trusting. After supplying a proof, the user is either allowed to post anonymously, can supply more required details, or even sign up to enable SSO with the site. Read on: Implementing Age Verification.
Switching email services
The user is switching an old email address for a new one. That old address had been registered with a mix of sites, some with and some without Yadis compatibility. After registering the email change at the users identity URL, the change is propagated to compatible sites and the user sees a list of all successful updates. A few important sites are missing or failed to update, so the user visits them and discovers two sites have implemented Yadis. Those are quickly added to the propagation list and succeeds update. Of those non-compatible sites, the user fixes some manually and forgets about another bunch.