I see a pose as the simplest component of an action. The pose identifies the major parts that are required for action. There must be an environment such as the stage that provides the context in which the action takes place. There is the physical structure of the actor doing the action. There are the joint angles that describe the geometric relationships between the elements of the physical structure.
I have greatly simplified everything, the stage, the body components of the actor, and the elements of the pose. However, all these pieces are directly observable, and they have to relate to one another.
Here, positions refer to actors on a stage, but could be generalized to other vertebrates in other settings. The core concept is to focus on the actor's centre of gravity. The relationship to the stage is represented by the plumb line of gravity. The body is drawn outward from the centre of gravity. Assuming a standing (supported) position, the height is calculated so that the support (e.g. the feet) is at the stage floor level.
In any position on the stage, standing straight, the actor can rotate.
The actor might lie down on his stomach, head facing the audience and feet away from the audience. If he started standing straight, facing the audience, he will have rotated about his waist, his centre of gravity - about an axis from one hip-joint to the other. If standing straight is an angle of 0, then using the same right-hand rule, his angle will have increased (thumb toward stage-right from the audience).
The actor might lie down on his left side, so that both head and feet are the same distance from the audience, but the actor is facing the audience. From standing straight and facing the audience, the actor has rotated about an axis from the belly button to the back of the spine. Again, using the right-hand rule, the angle will have increased (thumb toward back of the stage).
For purposes of illustration and experimentation, I treat position parameters as if they can be controlled, like the joint angles of a pose. In reality, the position is the result of action in conjunction with the laws of nature such as the force gravity and momentum.
I hope you will experiment with ridiculous positions such as having the actor upside down and floating in mid air.