12. A system for establishing a measure of an image-based semantic distance between a pair of semantic concepts, comprising: a general purpose computing device; and a computer program having program modules executable by said computing device, wherein the computing device is directed by the program modules of the computer program to, respectively compute a semantic concept representation for each semantic concept based on images associated with the concept, wherein each of said representations accounts for variations in the appearance of the associated semantic concept as depicted in the images used to compute the representation, and compute a degree of difference between the pair of semantic concept representations to produce said image-based semantic distance measure, wherein computing the degree of difference comprises computing a combination of the degree of difference between each appearance variation associated with a first of the semantic concept representations and each appearance variation associated with the other of the semantic concept representations.
13. The system of claim 12 , wherein said variations in appearance are attributable to at least one of differences in scale, orientation, object shape, illumination, color and texture.