Not all works of art represent something, but some do, and their doing so is relevant to our aesthetic experience of them; representation is ttherefore an aesthetically relevant property. Whether a work of art possesses this property is dependent upon context. Yet there are no clear criteria for determining whether context-dependent properties are present in an object, so there cannot be any clear criteria for determining whether an object qualifies as art.
An object may have some aesthetic properties and not be a work of art is a possibility that the reasoning above fails to exclude.