There is a list of class codes and their meanings published by IATA in one of their resolutions. Unfortunately, although most airlines stick to the "obvious" ones (e.g. F = First, C= Club) there are different amounts of variation in the back of the bus. One airline may use B for their deepest discount economy while another may use B for a changeable economy fare. I believe both Oneworld and Star have standardised class meanings across their member airlines but they don't both use the same definitions.