So, I'm writing an urban fantasy (think Dresden Files) and I want to have a world where there are an indeterminate number of magic systems, all supporting eachother in one way or another, and possible to group in any number of ways depending on your perspective. Anyway, the system I want to focus on is diagrams.
My idea for diagrams is that they're very specific geometric figures which invoke agreements with abstract entities. These deals can be set up by shamans, priests, summoners, diabolists, whatever, but they come down to an agreement whereby the entity agrees to cause such and such effect whenever a particular geometric shape is drawn and traced with activation dust. For example, a minor spirit of gravity might agree to power a small region of weightlessness when such and such diagram is inscribed. The price might be worship, it might be a symbolic offering of power, it might be an inch of height, it might be the chance to corrupt the negotiator with some measure of mental and bodily influence.
Anyway, I want to explore the way that, while there might be an official guide to designing these diagrams, in the end, it's really up to the negotiator what it looks like. I could draw some interesting parallels between this and language, I think.