36.1 What can be a group

[wybesse]

We had this conglomeration turn up in one of our armies during a battle and eventually concluded that it might be many things but that it would not qualify as a single group because of the gap between B and E, which would violate 36.1.c. Is that correct?

[David Kuijt]

Nope, that's a group. The gap only prevents groupage if there is no pathway without a gap that creates groupage. In this case, if C or D did not exist, then E would not be part of the group because of the gap between it and B.

To put it another way, group is a transitive relation. If A and B are a group, and B and C are a group, then A and B and C are a group. Or in your example, ABCDE are a group because AB is a group, BC is a group, CD is a group, and DE is a group. Therefore ABC is a group, CDE is a group, ABCD is a group, and ABCDE is a group (and some others that I've left out). But ABE is not a group unless you include C and D both. You can't move ABE as a group.

[Bill Hupp]

That's very interesting!

[wybesse]

Huh. All righty, then.

[David Kuijt]

Huh. All righty, then.

If the only way to transfer electricity from one stand to another was if they were in edge and corner contact and same facing, then it the easy way to determine a group would be to say if you shocked one stand, who would feel it? If every stand would feel the shock (passing through only stands in the potential group) then you have a group.

Needless to say, the other WGC luminaries shot down my suggestion to use that example in the rulebook explanation. They shot down my suggestion to use the example of a contiguous graph from Graph Theory even faster.

[Spencer]

Shocking!