Was working today to understand the General Transit Feed Specification. (This is the spec that Google uses to drive its public transit scheduling.)
I worked up this ERD/UML diagram. Helped me grok it. Thought it might help others as well.
Not entirely complete – I’m working to understand NY transit, and this is the subset that the MTA uses. If I need to, or if there’s interest, I’ll pad this out to be complete.