If I understand you right you are asking about the INTENTION of art. Now, this is a little complicated because on the one hand you got the artist who may have a certain intention with his work. Maybe he has got a certain message, maybe he wants to shock etc. But as soon as the artist delivers his work to the audience/spectators he LOSES CONTROL with it. Now - on the other hand - the audience/spectators take over, so to speak. They may pleased, they may be shocked, they may be happy, they may be angry, and the artist can do absolutely nothing about it. One thing is the INTENTION, another is the REACTION.
The intention of art may vary from artist to artist, and even from work to work. That's why it is so hard to define the intention of art.
As I said in my article http://hubpages.com/art/What-are-the-arts objecitve criteria for art is quite problematic becuase we got no "God of Art" to refer to.
So, If I am to answer your question, I'd say, that the intention of art is WHAT THE ARTIST HAS IN MIND when he creates his work. The reaction is quite another story