SR4, Sm (Street Magic), Au (Augmentation), Ar (Arsenal), Rh (Runner Havens), Ce (Corporate Enclaves), Em (Emergence), Un (Unwired). Easy, right? Ok, so I made them all up.
...apologies, it is the Scientist in me that recognised the elemental translations because of the upper+lowercase format. Was just making a funny that's all.

QUOTE (nathanross)
So far my group has never once used a Canon plot.
...true, But there still is the Canon background & setting. At least I try to keep that in mind while writing the plot.