Sorry, I was assuming readers knew about Crossrail - which was presumptive. Note that the DLR shares stations with the pre-existing Underground system, and has

Sorry, I was assuming readers knew about Crossrail - which was presumptive. Note that the DLR shares stations with the pre-existing Underground system, and has platforms at different levels, but is still considered a separate system not part of the system. I think the desire to see the greater system decomposed into various properly named subsystems in the most coherent way possible is something that is characteristic of a software development mindset.