I'm pretty sure philosophers invented metadata, even though they did not give it that name. The question how to distinguish between the properties an object has

I'm pretty sure philosophers invented metadata, even though they did not give it that name. The question how to distinguish between the properties an object has and what properties we attach to it, is sort of central in epistemology. Higher category theorists sometimes distinguish between stuff, structure and property http://nlab.mathforge.org/nlab/show/stuff,+structure,+property http://nlab.mathforge.org/nlab/show/stuff,+structure,+proper..., which makes the definition of forgetful functors more precise. Conversly attaching structure or properties are (not nescessarily unique) adjoint functors to those forgetful ones. In mathematics this comes up for example if you consider the category of abelian groups from which there is both a forgetful functor to the category of groups and to the category of sets, but the general idea should be applicable to metadata attached to text aswell.