architecture vs sculpture

ON "Principles of Architectural History", Paul Frankl states that "People are part of architecture", and "this too distinguishes architecture from both painting and sculpture, from we do not stand in front of a building but are surrounded by it. "(P159) Later, he added:" a painting can be interpreted and brought to life again, because the figures remain in it always. a building dies as soon as the life within it has vanished, even if we know the custom of the people who once belonged to it."
I think Prankl brings an interesting question to us: how do we distinguish a sculpture and an architecture, if the size is not a matter?
On "The Essence of Architectural Creation", the author brings a defination of an architecture. "Our sense of space and spatial imagination press toward spatial creation; they seek their satisfaction in art. We call this art architecture; in plain words, it is the creatress of space"(P287)
Before this class, i don't really think about architectures or sculptures. I did some installations but I am not sure if they were "sculptures"? And, how to distinguish an installation and a sculpture? I think with sculpture, you create a form from the same medium. either you take away from the medium, as in a block of stone, or you collect together pieces of the medium, as can be done in clay or glass. But architecture is different. The result of architecture is a collection of different materials. An architecture is a system that connecting disjoint things in useful ways.