@pislikeller: This is a common notation for sound changes. See https://en.wikipedia.org/wiki/Sound_change#Formal_notation for more.
@chridd: Do you accept suggestions for sound changes to be added? I noticed that the (well-established) sound change from Proto-Semitic initial *w to North-West Semitic (i.e. Hebrew, Aramaic etc.) *j is not included. For a reference, see e.g. "The Semitic Languages: An International Handbook" by Weninger et al., p. 432.