A lot has been written (and standardized) about Open Identity protocols, transport binding and token format, (things that are primary concerns of IDPs - IDentity Providers). However I feel less attention has been paid to changes that Relying Parties (RPs) have to make to their systems (user experience and design, identity and account structure, session management etc.), after all there is a big difference between provisioning your own identity and performing your own primary authentication, v.s. relying on some one else to do it for you.
Here is a list of 10 things (you know it had to be 10 !) that you need to think about and decide if you are planning to be a Relying Party:
1. Decide which IDPs to accept: Not all IDP are created equal of course.
2. The design of the sign-in and registration page: in way that encourages the use of OpenID but not confuse users who do not use OpenID or do not know what it is.
3. Covering the "Information gap": How to capture information you need and is not provided by user's IDP during initial session, also determining whether you can call IDP (thru back channel) and ask for more (or updated) information about a user.
4. Privileges: Decide whether an OpenID user of your site has all the privileges of a local user or do they need to create a local account before they can perform certain activities.
5. Covering the "trust gap": Do you need IDP to provide some level of assurance (or verification) of the attributes it is providing you. For example if IDP provides user's home address, do you need this address to be verified?
6. Account Linking - decide whether you plan to become a true RP (i.e. no local account with local user name and password) or upon initial OpenID session, you plan to ask user to "register" with you site and create a local user name and password.
7. Session Management:Do you plan to sync you local session with IDP session length (or shorter or longer?) regardless will you "force re-authentication" for certain activities?
8. Profile Change Management: How do you plan to deal with users' who lose/forget their OpenID, is it important for you that a user
9. Account Cardinality: How many local account will you allow to be associated with one OpenID identifier, conversely, can an OpenID account be associated with multiple local accounts?
10. Logout: Whenan OpenID user logs out of your site, are you planning to report that to IDP for federated logout?
And if you are looking for controversy, consider the issue of "reporting adverse behavior" i.e. if a RP experienced an adverse behavior from a user with OpenID, should the RP report it to the IDP? If you consider IDPs equivalent to robots then, it seems like the Three laws of Robotics says no, but if you think of IDP more like credit bureaus (or evolving to become more like identity bureaus) then the ChexSystem indicates otherwise....
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Courtesy:http://softwareforallseasons.blogspot.com/search?updated-max=2010-04-19T10%3A46%3A00-07%3A00&max-results=7