A program that consists of a chain of objects. Every time a new object is added to the chain, it is placed on both ends of a the chain. Each object then begins to sort itself down the chain until it finds the right spot and is joined by its twin. Along the way it picks up a reference to each other object that shares a related characteristic. The twin objects then merge into one, combining their object collections. That way each object found already stores the entire chain that is like it. Find one, link to all.

A program that consists of a chain of objects. Every time a new object
is added to the chain, it is placed on both ends of a the chain. Each
object then begins to sort itself down the chain until it finds the
right spot and is joined by its twin. Along the way it picks up a
reference to each other object that shares a related characteristic.
The twin objects then merge into one, combining their object
collections. That way each object found already stores the entire
chain that is like it. Find one, link to all.