As one gathers facts and gains understanding of the subject then there is a gravitational pull towards a finished piece. The outcome may be inevitable for a particular person, but since each person brings different experiences to life, the resulting waterfall can draw them to a different endpoint. I couldn't help but think of Frank Lloyd Wright's Fallingwater home outside of Pittsburgh. My spouse and I visited there this summer. The home was constructed by layering and cantilvering the floors of the house.
Composing is both formulaic and creative.
I like the visual connection with Fallingwater. Like the waterfall changes shape, size, energy, etc. Just as if I fall of the cliff into the water, it pulls me along, so too does writing work its magic on me that way. Often, I find myself writing something completely different than I planned to write, no matter how much I plan, organize, invent, think, etc. In this way, writing and the language I rely on to write often guide me through the process of composing.