A lot of the confusion comes from the desire on the part of many (including, apparently, Umberto Eco) to preserve the notion of art as expressive. There's good reason for that, from an aesthetic viewpoint, because it distinguishes objects that are "art" from objects that are purposive or otherwise practical or incidental adornment or whatever sorts of things we want to see as normally meaningless but necessary or useful. So, the art object is meaningful, that meaning is artistic expression, and the artist is the one doing the expressing via whatever medium chosen, to create the meaningful object. It's like a dog chasing its tail - all to preserve a miniature model of God creating the world.
Another way it is expressed is as the artist has an Idea (with an upper-case i, signifying that it is actually a little spiritual and mystic in nature). The artwork is an expression of that Idea. The vehicle of expression is intent - the gas that vehicle uses is ability.
Unfortunately, these bright and shiny notions don't seem to have much to do with meaning. If you think about the way a sentence is meaningful, you can assign an intent to the writer that is roughly equivalent to the meaning as you understand it. But no amount of intent will make an unintelligible sentence (say, one made up of random scribbles that happen to look like words) meaningful. In order for my sentence to mean what I intend it to, I need to construct it in a way and using words that are already meaningful to whoever reads it. This correlates to my having an idea (lower case i) that I express (however I want) using symbols that are already meaningful. That can be seen as how meaning in art works, but it becomes a bit of a stretch once you get past the point of straightforward representation.