The notation is based on Larry Morris' hand drum notation, found at the Groove Archive, and Drums and Percussion Page The only difference is the | (vertical bar). Larry uses it to indicate the first beat in a bar, I use it to separate bars or fractions of bars, just to increase readability.
o = open s = slap b = base of,sf = open flam, slap flam _ _ = over a note means use your strong hand, e.g. o | = bars * = pulse . = rest >> = the rythm continues on next line