SimonFa, on 2012-April-28, 14:00, said:
What about UI? Partner may have made a natural bid based on us not having discussed the situation.
In my experience, there are a few things you can be fairly safe assuming with any but the most inexperienced partner. They include Stayman over an opening 1NT (though not necessarily over an overcall, especially if you partner is a rubber bridge player), some sort of Stayman over an opening 2NT, and the Unusual NT.
When playing with inexperienced partners I always start by asking "transfers or no transfers?" If the answer is "no transfers" I ask "what about Stayman?"
To return to your question, we have the EBU regulation quoted above telling us to alert things that we intend to treat as alertable, even if not specifically agreed.
I often say something like "we have no specific agreement about this, but I think the usual treatment of this call would make it alertable", or "we haven't specifically agreed this, but I think it follows from our other agreements that it will have an alertable meaning".