Consider this simple situation where three edges connect at a node:
I’d like to write a succinct and clear description of the relationship between A and B in such a way that differentiates it from the relationship between A and C. Something like “when traversing the node in the clockwise direction, A is adjacent? to B, but A is not adjacent? to C.” But it’s not really adjacency.
Said in a different way: imagine you’re standing on the node and you’re facing towards A. You start spinning yourself clockwise. The next edge you’ll come to is B, not C.
Is there a way to describe this relationship between A and B in a more succinct, formal, or correct way than I’ve written above?
It must be directional (one relationship of this type exists in the clockwise direction from A, and another exists in the counter-clockwise direction). And it must scale up to cases where more than three edges are connected at the node. Maybe it has something to do with routing? (I am thinking about this in the context of road networks.)
Two approaches I’ve tried already but haven't gotten far with:
9IM-like topology references: I’ve looked at the DE-9IM, and even though I'm not a mathematician, I think I can still tell from the diagrams and terms that it doesn’t cover this type of relationship. Neither do I find it yet in the topology descriptions at the ESRI help or Oracle help. (Maybe there's something there but I'm just not finding it yet!)
Faces: I’ve played around with the fact that the face on the “north” side of A might also bounded also be by B, but not C. However, as you can see in the diagram here, that’s not always true. Imagine my diagram is an extract from a road network where A and C are arterial roads and B is a short dead-end road.
I suspect there may not be a single term for what I’m trying to say; at a minimum I’d like to be able to describe such a relationship in a simpler way than I’ve done above. This is a platform-independent question. Right now, I’m just looking for the right words. Later I will try to implement the concept in python (pyqgis or arcpy) on a shapefile, so any answers with that end point in mind will be particularly interesting, but not necessary.