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logical: adj.

[from the technical term logical device, wherein a physical device is referred to by an arbitrary ‘logical’ name] Having the role of. If a person (say, Les Earnest at SAIL) who had long held a certain post left and were replaced, the replacement would for a while be known as the logical Les Earnest. (This does not imply any judgment on the replacement.) Compare virtual.

At Stanford, ‘logical’ compass directions denote a coordinate system relative to El Camino Real, in which ‘logical north’ is always toward San Francisco and ‘logical south’ is always toward San Jose--in spite of the fact that El Camino Real runs physical north/south near San Francisco, physical east/west near San Jose, and along a curve everywhere in between. (The best rule of thumb here is that, by definition, El Camino Real always runs logical north-south.)

In giving directions, one might say: “To get to Rincon Tarasco restaurant, get onto El Camino Bignum going logical north.” Using the word ‘logical’ helps to prevent the recipient from worrying about that the fact that the sun is setting almost directly in front of him. The concept is reinforced by North American highways which are almost, but not quite, consistently labeled with logical rather than physical directions. A similar situation exists at MIT: Route 128 (famous for the electronics industry that grew up along it) wraps roughly 3 quarters around Boston at a radius of 10 miles, terminating near the coastline at each end. It would be most precise to describe the two directions along this highway as ‘clockwise’ and ‘counterclockwise’, but the road signs all say “north” and “south”, respectively. A hacker might describe these directions as logical north and logical south, to indicate that they are conventional directions not corresponding to the usual denotation for those words.