Alex Weldon: I forgot to mention that it also works as a tesuji for connecting groups. There's a good example in Tesuji and Anti-suji of Go, but I'm flipping through the book and can't find it, so I'll try to recreate something similar from memory:
connects unfailingly (if White a, Black b, if White b, Black c), although here the shape looks more like a "big dip" than a bulge.
HolIgor: Please, indicate a and b. There is no connection here. See the diagram below. One has to make black's stones at the top less vulnerable.
Alex Weldon: Ah, yes, sorry. Two mistakes. I forgot to put a and b, and you're right that I gave Black's top stones too few liberties. Fixed now.
John F. I imagine it was you who deleted my comment, but your original diagram was fine and the connection is secure. Black answers a one point above, not at b. It is that move that is the point of the tesuji. But if you are going to insist on the less interesting version, you need to change the second diagram as well.
Alex Weldon: Sorry about that. Somehow, I misinterpreted what you were saying. Now I see your point, and think you're correct that the original was fine. I guess I should restore the original, remove all these comments, and fully explain the variations that preserve the connection. However, being weaker than both you and HolIgor, I'm not confident in saying you're right and he's wrong, so I'll hold off on doing that until a third, stronger player confirms one way or another, or the two of you agree.
Bill: Is there a connection here?
Charles See keima side connection. There is an obvious point about how many stones of the other colour one allows, while still using the same name for the shape. All I can say on that is that one should stop using the name when it stops being useful to think of the shape in the same 'cluster' of ideas.
Alex Weldon: Well... the keima side connection and big bulge aren't just related by the relationship of the stones, exactly. Both seem to have the purpose of establishing a firmer connection between two existing stones with an ogeima relationship. But you're right that it's being used in a completely different context. Maybe we should remove this whole section and just leave a note "See keima side connection for the same shape applied in a different context."?
Charles I wouldn't see any need to remove anything. Is this diagram a case of 'big bulge' or not? It's really the wrong question. Thinking of three stones as a unit is probably an advance, and demarcating when names apply can come later, if at all.