Fortification

Roles: citadel, wall, gate, defender, attacker, siege, garrison, provisions

Defensive military architecture — walls, towers, gates, moats, and the tactics of siege and defense. As a source domain, fortification foregrounds the boundary between protected interior and hostile exterior, the asymmetry between attacker (who must breach) and defender (who must hold), and the critical vulnerability of the gate (the only permeable point in an otherwise impermeable barrier). Structurally productive because it encodes the idea that security comes from controlled access rather than from eliminating threats, and that the strongest wall is useless if the gate is opened from within.

As Source Frame (1)