fields:

<field name="Theme"/>

<field name="Time"/>

<field name="Place"/>

<field name="user_id"/>

<field name="date_deadline"/>

<field name="Docs"/>

<button name="register" type="object" string="Participate" class="oe_highlight" Confirm="Are you sure?"/>

I want to set user1 to get the security write access of field "time","theme"; user2 to "place" "user_id" and all users can execute the button "register"; how shall I set?