Interlock
Every group shares a member with every other; stop when a decision in one has reached all without a plenary.
Paxos: any two deciding groups share a member.
Seen in Denis Blanchot, Dobble (Spot It!), 2008–09, after Jacques Cottereau (1976)
Try it on your work
Divide the thing you're working on into sub-assemblies. Require that every sub-assembly share at least one component with every other. Stop when no two can be changed independently without the shared component registering it.
Write your project as four sections for four readers. Require every section to contain at least one sentence that also appears in every other. Stop when a change to any one section would contradict the others unless they move too.
When people split into working groups, require each group to contain at least one person from every other group. Stop when a decision taken in one group has reached every other within the hour without a plenary.
How it has been used
Consensus systems such as Paxos use quorums that intersect. Any two groups large enough to decide must share at least one participant; that overlap carries knowledge of what has already been accepted, preventing separate groups from finalising incompatible values. Agreement is protected by the geometry of valid coalitions, not by requiring everyone to meet at once.
Where it leads
Grouped under Help the parts work together