There are those who would say that true art would define the cow and differentiate it from the kangaroo.

"Performance Art", if only done once, isn't art. It's ego on display. "Hamlet" is art because it allows actors and directors to work within a the discipline of the play to create their own vision of what is going on. A single piece, done once and then tossed aside, doesn't communicate.

And as much as I hate to agree with Amos, art IS AND HAS to be communication: with the present and with the future within the context of the past. (I might agree with Amos, but I thought of it first.)