Transition Engineering: Engineering the Passage from a Current Condition to a Prepared Event Boundary

A system may possess a representation of a possible future condition without possessing a structurally available passage toward that condition. The distinction becomes acute when a future event requires a prepared entry condition before execution can begin. This paper proposes Transition Engineering as the study and engineering of the passage from an actual current condition S0 to such a prepared entry condition A, through intermediate conditions S1, …, Sn-1 whose attainment progressively alters what the system can do. The central propositions are that representation does not establish access, and that access to an event boundary does not determine what occurs beyond it. The paper develops a formal apparatus comprising reachability, dependency sets, a four-status taxonomy of edges, blocked and branching passages, critical dependencies and mutable state spaces, and it defines the closing operation of a transition as the verification of a gate. Four design principles for gates (testability, conjunction, placement before the point of no return, and enforceability) are derived and examined against a documented field case, the stabilized-approach gate of commercial aviation, which separates failures of specification from failures of obedience. A constructed human-scale illustration and a programme of validation are given. The resulting architecture, S0 → ⋯ → A → C(open) → B, assigns the passage to A to Transition Engineering and the conditions surrounding the event to Event Engineering, while leaving execution open.