This pivotal fourth principle of CPM is where Petronio moves from being descriptive to prescriptive. With the first three principles she’s been mapping out how people handle their private information—they think they own it and they control it (Principle 1) through the use of privacy rules (Principle 2). If they disclose some of that private information, the recipients become co-owners of a patch of common informational territory, which entails both rights and responsibilities (Principle 3). Principle 4 assumes that the privacy boundaries co-owners place around this particular piece of information won’t necessarily look the same. But she thinks that for the sake of relational harmony they ought to be congruent, so this principle is a plea for co-owners to negotiate mutual privacy boundaries . Or, using the map metaphor, she urges parties to collaboratively draw the same borders around their common piece of informational real estate