Clause 4.1 opens the principle set. This clause introduces the principle set. What the structure shows is that every later principle is presented twice: a short principle statement in the first subclause and the reasoning behind it in the second. A programme that wants to apply the principles should read each pair together, because the rationale explains the boundary of the principle.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.