Obviously virtual assistants should ask for clarifications. Now imagine every time you ask for the time, weather or a flight to London and you always mean only London UK, imagine how annoying that can be. Makes me wonder if VA's are more productive in such cases compared to typing.

"The time in London, England, is 8:23pm."

"No, I meant the time in London, Ontario"

"Sure. The time in London, Ontario, is 3:23pm."

You start by doing a best guess, and actually listening for a correction. For other kinds of requests, you reply with a best guess and ask for confirmation or for clarifying questions.

Hard, yes. Not impossible.

Right. A good test for a conversational AI is whether it could perform the Abbott & Costello “Who’s on First” sketch with you. It should make assumptions where the characters in the sketch make assumptions, and ask questions borne from confusion where the characters do.

"The average time in London is 5.53 pm"

I mentioned in another comment that with Siri, this exchange does work:

“What time is it in London?”

... gives answer for London Ontario

“No, London England”

... gives answer for England

However there’s no memory to this; the same thing happens next time you ask.