You were putting the A40 Farina (you see we need this to properly indentify model, even though it is not it's "official" name) as Supermini, but I think it should really be Sedan.

A40 is 3664 mm long < http://www.carfolio.com/specifications/models/car/?car=50457&Austin >

4-door hatchback ("5-door") should not be mixed with coach and coupe anyway.

I meant, added into one catagory. Like:
"Coupe, Hatchback, coach" or something.

And sedan or saloon have their own catagory, and not have it shared.

what do you mean by "should be added"? there are already hatchback and coupe categories.
Coach was suggested but rejected, and currently are listed in hatchback & coupés.

For the A40, is it a sedan or a supermini? What is the length of the car? I was putting in supermini the cars that were less than 3.5m

I think that coupe, hatchback and coach (although I've never heard of this term before) should be added. As they are all so close. And sedan should be all it's own, as it is probably the biggest catagory.

A40s - http://www.imcdb.org/search.php?resultsStyle=asList&makeMatch=2&make=&modelMatch=- 0&model=a40&modelInclModel=on&modelInclChassis=on

Some appear as "sedan" others as "Supermini".

"Trucks" categories are for heavier trucks. "Lorries" in UK-English.

While on this subject, I wonder why pickups, vans and SUVs are not in the truck category rather than cars.

You think it would be simple ? And what about the new types created by the makers, like the "coupéspace" which is a 2-door "monospace" (french "monospace" = minivan, I guess. Like the Chrysler Voyager etc.)
That's the name used by Renault for their Avantime.

On that list there are too many body types. It is not useful to separate cars in so many categories.

I do not know if we could group sedan and 5-door hatchback. They are usually similar. 3-door may often look more like a coupé than a sedan. And there is still the problem of cars like the VW Beetle: it is not a hatchback, it is not really a coupé, not really a sedan

This discussion could go on forever as there are many, many terms used. See: http://en.wikipedia.org/wiki/Car_body_style

It may be better to simply to use the type assigned by the maker.