Before using no-waste allocation to restrict the constraint domains, there is one constraint graph vertex for each of . Every distinct pair has a disjointness binary constraint, and also the two directional envy-free allocation constraints. Thus the constraint graph is the complete graph , with all ten edges.
The nonempty-bundle and no-waste allocation requirements are unary and add no edges. The original all-item coverage constraint has been removed because this variant permits unallocated items.
Figure 1.
The allocation constraint graph before restricting the constraint domains
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Restrict each agent to nonempty bundles of items that they value positively. Let the positive-value supports be
The residual constraint domains are , with sizes , respectively. The no-waste allocation and nonempty-bundle requirements are now built into these constraint domains.
If , every pair , is disjoint. Moreover, , so both envy-free allocation inequalities hold automatically because all values are nonnegative. Thus all three binary constraints disappear for the pairs
The only positive-support overlaps, and hence the remaining constraint graph edges, are
where parentheses list the shared items.
Each listed pair really retains restrictions. For , , , , respectively, let both endpoints choose , , , : this violates disjointness while belonging to both residual constraint domains. The directional envy-free allocation inequalities are also individually nontrivial. For example, for , choosing and makes envious, while choosing and makes envious. The analogous shared-item comparisons apply on the other three edges.
Figure 1.
The residual allocation constraint graph; labels show shared positive-value items
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