SQL Deadlock graph – arrows

In a SQL deadlock graph the direction of the arrows is an interesting thing.

With my mechanistic head on, I am imagining it as …

1. Spid-a requested a lock, and then got a lock (a two-way trip)
2. Spid-b requested a lock, and then got a lock (arrow ends-up pointing at spid)
3. Spid-a requested a lock, and is waiting (a one-way thing)
4. Spid-b requested a lock, and is waiting (arrow pointing away from spid)