I could announce to my family that our taxi has arrived for our trip to the railway station.
It would also be valid for me to state that an intricate contraption made of metal, rubber and plastic, with 4 wheels, a roof and a window, operated by a contractor, has arrived to pick us up and drop us at a place where trains arrive and depart on a schedule. Of course, I could then go on to describe what a train is.
There are infinite ways to communicate the arrival of a taxi. Yet, since everybody knows about taxis and railway stations, the optimal way to do this is in a short, crisp sentence. All other details are distractions.
Communicating the arrival of a taxi is trivial. Yet, we are all to prone to forget that effective communication is all about finding the right level of abstraction for a certain audience.
Observations 