This work proposes an operational definition of the black hole interior within a semiclassical effective framework. Rather than introducing a new fundamental theory, we clarify how existing concepts—such as quantum extremal surfaces (QES), island prescriptions, and boundary-based information recovery—can be consistently organized into a minimal definitional structure. The interior is defined operationally as a region whose degrees of freedom are not identifiable via volumetric localization but only through information-theoretic distinctions accessible from the boundary. This note aims to fix terminology and assumptions to facilitate future discussions, rather than to claim novel dynamics or mechanisms.
Osamu Tsutsumi (Fri,) studied this question.