We have a Siebel CRM and OPA integration requirement as mentioned below.
Rulebase has multiple screen pages and each page is to be filled up by different users. User 1 answers screen 1 (submits and closes the application) and User 2 or any other user resumes the previously saved session by user 1 and answers screen 2. When User 2 resumes the session, the screen 1 test user is also updated with current user log in name i.e. with User 2.
the screen1 test user = Login User
In the next rule document
the screen2 test user = Login User
Similarly for all screens..
How to check and restrict that known values should not be updated or re-assigned? Is there a possibility?
It's not very clear what you're wanting to happen here. But if you are using the same attribute on both screens then of course it will show the same value.
If you want it to show different values then you will need to assign different attributes and have the mapping handle the difference (ie the integration layer will need to handle that when user 1 starts that it sets the value for "the user 1 identity" and then when user 2 starts it will set the value for the completely other attribute "the user 2 identity").
If you want OPA to show 2 different things then you will need to give OPA 2 different things to show. Remember that OPA is stateless - something else needs to "remember" that you had user 1 here last time.