Is There a Framework for Systems Theory?

A theory is the underpinning of a methodology and a methodology is essentially a framework. So you could argue that Zettelkasten is a framework for applying systems theory and note taking. The perfect example in organization is obviously power GTD and all the other PPV and horizon, the rest of them. They're all frameworks under under like underpinned by a theory. But that theory could then have multiple Frameworks as well. Does that make sense? Yes.