The procedures are the standard ones for Burning Wheel, or Prince Valiant, or a 4e D&D skill challenge. There are parallels in AW and DW, though they're not identical.
The GM frames a scene, in accordance with principles that establish how this is to be done - those principles relate to player-established priorities for their PCs.
The players declare actions for their PCs, that engage with the framed scene. If the player succeeds, the rules indicate what happens next - generally the PC succeeds at their action. (In AW and DW it's sometimes a bit more complicated than that.)
If the player fails, the GM narrates a consequence that negates what the PC was attempting to achieve. In AW/DW, this is the time the GM makes "as hard and direct a move" as they like.
At all times - framing scenes, establishing consequences - the GM is obliged to "make a move that follows", That is, the fiction is a constraint. So are the player-established priorities. Further constraints are likely generated by the local, particular details of the action declaration.
In this sort of RPGing, there is not "collective authorship", any more than a D&D combat is collective authorship. The procedures make sure of that. Sometimes the only thing that follows is something that no one at the table would author were they free to author as they like.
The system of constraints, and the narrations that they permit and oblige, are the analogue to the inference rules of mathematics or of law. Obviously they are different sorts of inference rules, operating on different material and in a different domain. The participants need to be on the same page even moreso than in law (which requires more same-pagedness than mathematics) - but then, that is generally true for any successful RPGing.