Much useful insight can often be gained by comparing the attributes of objects with those of other objects in close proximity. The behaviour of a person on a crowded street might be explained in terms of the proximity of other people; the price of a house might be due in part to the existence of expensive homes in the immediate vicinity; and an area might find its homes losing value because of proximity to a polluting industrial plant. Location establishes context, by allowing distances between objects to be determined, and by providing information on their relevant attributes.