We talk about it like we know what it is, but what IS it?

I've struggled with this and submit this straw man as a starting point:

Frame is your worldview. Not merely what you think the world IS, per se, but the way you think the world ought to be. When something is not right with your world, it is Out of Frame. But it's also the ruleset you live by. The way YOU make YOUR world work.

So when we say "holding frame" with a woman, we mean following the rules YOU have laid down. SHE has entered YOUR frame. You cannot control HER per se, but you can control how YOU react.

Discuss