chronological order is the reverse order of necessity.

I walked into the forest, I gathered sticks, I created a woodpile, I made some kindling, I lit my kindling on fire, I nurtured the flame, I blew on it gently, I turned it into a stable roaring fire, I sat next to the fire, I got warm.

I'm cold; warmth solves that; a stable fire is warm; a stable fire grows out of a small one; kindling helps me start a small fire; I need kindling and wood; kindling and wood comes from trees; trees are in the forest; I should walk into the forest.

At any point, the flow of logic from the necessity/problem can branch:

I'm cold; warmth solves that; a stable fire is warm; a stable fire comes out of my gas fireplace; I should turn my gas fireplace on.

Problems are singular, and solutions are varied. The exploration of all possible answers to a solution thus looks like a tree branching outwards. This is the exact mirror of an ishikawa diagram, in which the complexity of factors contributing to a diagram looks like a tree branching outwards, but in the other direction.

In the center of this diagram is a problem, or a supposed problem.