Mapping a gas station / convenience store

I've seen this done in almost every combination imaginable, and would like to know what the 'correct' way to do this is. I've seen the building marked as 'retail' with a point at the pumps for 'gas station' and a point in the building for 'convenience store', I've seen the building itself marked as one with a point added for the other, I've seen the pumps area marked as the gas station and the building marked as the convenience store, and on and on.

What's the recommended way to do this?