This is really basic (I'm new to this stuff), and doesn't even matter at all - But I'm just curious:
From my book:
If $R = (G,A,B)$ and $S = (H,B,C)$ the composition of $R$ and $S$ is known as $S \circ R = (H \circ G,A,C)$
First of all, if it says "of $R$ and $S$" I'd expect the $R$ to come first, and then the $S$. Which is not the case in $S \circ R$.
Even the graphs are inverted. I would expect $G$ to come first. But we got $(H \circ G,A,C)$.
I can live with that. But I'd like to know why is this the case. Why are they inverted?