Amy Gahran, “Stepping Off the Relationship Escalator: Uncommon Love and Life”

Rules, agreements and boundaries

Unlike rules, agreements apply only to the people who participate in these negotiations. Agreements are never presented to third parties as take-it-or-leave-it choices. All parties are empowered to renegotiate existing agreements that may no longer fit well.
...
A personal boundary is an individual opt-out decision. Any individual may set their own boundaries, regardless of relationship style or status. A boundary is set when someone clarifies which situations or activities they personally plan to avoid.