Did you have a look at the documentation on OTN?
google: "Interview services of OPA"
Hope this helps,
Thank you for the update. However by any chance do you have any PDF to share across. There are some limitation around my side to view above sites.
Thanks n Regards
The Developer's Guide that Darko linked to is contained in the zip file you download to get OPA Determinations Server (which provides the interview service). There is no published PDF format for this documentation.