difference between http://schema.openid.net/contact/email and http://axschema.org/contact/email

Question

when to use http://schema.openid.net/contact/email and when to use http://axschema.org/contact/email in openid request.

Answer 1

Unfortunately there is no standard schema for Attribute Exchange (AX). But the axschema.org seems to be the closest thing to it. To know which one to use, the best way I know of is to look for a "hint" about which schema(s) are supported in the OP's XRDS document. DotNetOpenAuth does this, for example, and has a good success rate. When the XRDS doesn't contain any of the AX schema URIs, you can send all three (yes, there are three) AX attribute URI formats to best ensure a useful response.