How assign CO's to respective users at Portal

Hi Friends,

I have developed a webdynpro application with GP Interface,

I have 3 callable object corresponds to three Views.

Now I want that whenever a user logs in to portal, only the respective View should be visible to him, not the whole process/application, if it is available,

<b>For example:</b>

if <b>user1</b> initiates the process with view1 then he should not be authorized to view second view2.

when User2 logs in , he should see the View2 with the data entered by user1 if entered, else a message like <b> "The process has not been initialized"</b>

Can you suggest me how should I approach,

Thanks & Regards:

Deepak