So if thats postmodernism.. what is art and who decides??

We read about postmodernism so now we should have a new sense of what art is and who decides. And I would say that I do. I know now that postmodern art is about a mesh of all sorts of ideas and styles and people and places and events. It is about the coming together of everything and the movement of creating something out of other thngs. I think that this tells us that art is a collage so to say and that the people who decides are to postmodernists themselves. The modernists and the premodernist arent going to agree on what art is and what is or is not art. Because of this I think that postmodernists are the ones who decide what postmodern art is and the modernists decide what modern art is and so on and so forth. It is still a touchy subject though and I still cant completely wrap my head around all of the concepts but I think nonetheless I have gained a greater insight from reading this book.