IDP Service

1) Has anyone has experience in building a common IDP service? What are
the issues? I think the business "agreement" of a common domain is
challenging part. 

2)  Is there a profile for IDP <--> IDP scenario. I am
talking about a case where there are more IDPs and few SPs are
participating. For example, if a user is logged into IDP1, and clicks
on a  URL to a SP (which also acts like IDP), you can bypass the
<AuthnRequest> i.e., generate the SAML Assertion and send it.

Let me know if this is not the right forum to ask these questions. 

(New to this TC).

Thanks,

/Prasanta