Lets say you have a wall with a door in it (a single entity). If the wall/door does not have an animation attached, it cannot be opened. However, if you have a model of a wall with a door opening, then you can insert a door (as a separate entity), and a LUA script (attached to the door entity) can rotate the door so it opens and closes.
"THERE IS NO SPOON"
AMD 6300 6 core 3.5 ghz, Windows 8.1, 8GB ram, GTX 650 2GB ram