In geographic information systems back in the 1970s, we used to use a term
"half-neighbor". In a checkerboard, each square has 4 'full neighbors' (of
the opposite color to the current square), and four half-neighbors (same
color), for a total of six neighbors. Just as each brick in a wall has
six neighbors.

David

On Tue, 16 Apr 2002, granthutchison wrote:

> > The question I pose is this: can a point, more specifically a
> > quadrapoint (quinta or even more), also be a border? Take Four
> > Corners, USA for example. Is it correct to say that New Mexico and
> > Utah 'border' one another? Or Arizona and Colorado?
> Like you, I've puzzled over this, with reference to Jungholz and the
> other exclaves that join the parent country at a single point.
> My take is that the two entities don't adjoin each other at all,
> since the length of their border is zero - the same as the length of
> any border for any other two non-adjoining entities.
> But this leaves me with an odd problem when I'm counting
> international border segments around Jungholz, and other exclaves
> that are joined to the parent country by a single point. From inside
> Jungholz, there is a continuous border with Germany. And from
> Austria, there's also a continuous border with Germany. But on the
> German side, there's a discontinuity - Germany borders Austria, then
> an Austrian exclave (Jungholz), then mainland Austria again.
> So Germany counts three border segments, but Austria+Jungholz count
> only two. Hmmm. That upsets me, so I have to revise things and say
> that the border between mainland Austria and Germany is in two
> discreet segments, separated by the quadripoint with Jungholz.
>
> So that's what I think. Anyone else?
>
> Grant
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