Changes

For example, overlaying the corresponding [[dual graph]]s on the plane-embedded graphs shown above, we get the following composite picture:

For example, overlaying the corresponding [[dual graph]]s on the plane-embedded graphs shown above, we get the following composite picture:

[[Image:Logical_Graph_Figure_4.jpg|center]]

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Though it's not really there in the most abstract topology of the matter, for all sorts of pragmatic reasons we find ourselves almost compelled to single out the outermost region of the plane in a distinctive way and to mark it as the ''[[root node]]'' of the corresponding [[dual graph]], indicated in the above Figure by the ''amphora'' or ''at'' sign, "@".

Though it's not really there in the most abstract topology of the matter, for all sorts of pragmatic reasons we find ourselves almost compelled to single out the outermost region of the plane in a distinctive way and to mark it as the ''[[root node]]'' of the corresponding [[dual graph]], indicated in the above Figure by the ''amphora'' or ''at'' sign, "@".