In possible world semantics for propositional calculus, possible worlds are usually taken to be models for propositional formulas (the set of valuations in which a certain formula is true)
In first order logic, is the proposition expressed by a sentence a set of valutations?
For instance: "Fa" expresses the proposition that is identifiable with the set of valuations that make "Fa" true, or the propositin is the set of structures <D,I,v> where D is a domain of possible things, I the interpretation function that assign the extensions of predicate letters and v the valuation function that to every formula of the language assign a truth value considering the extensions of the predicates given by I and the objects in the domain?
In short: in first order logic, are propositions expressed by sentences the set of structures in which the sentences are true?
IN this sense, in the context of FOL, are possible worlds just various structures <D,I,v> ?