Interfaces, Contracts & Hidden Implementation

Primes about separating an observable contract from the implementation behind it: abstract data types and the open-closed principle hide internals behind a stable surface, while confused deputy, observable-surface-becomes-contract, and refactoring examine how authority, dependency, or structure shift once that boundary is in place.

15 primes in this family — primes that sit near one another in abstraction space (k-means over structural-signature embeddings). Each is shown with its short description.

• Abstract Data Type — Specify a component by its externally observable behaviour while suppressing its implementation, so any conforming implementation is interchangeable behind the contract.
• Adjacency Pair — A typed first move that conditions a second and makes its absence noticeable.
• Aspectual Individual — Treating a single underlying entity, under a fixed role or aspect, as a distinct derived bearer of properties with its own narrower existence conditions.
• Client Server Model — An asymmetric request-response relation in which one party holds a capability and many others initiate to consume it.
• Confused Deputy — A privileged intermediary acts on its own authority while the intent originated with an outsider who lacks it, so authority is borrowed without intent being tracked.
• Law of Conservation of Complexity — Every problem has an irreducible complexity floor that design can shift between parties or moments but cannot reduce below the floor.
• Message Passing — Autonomous holders of private state interact only through discrete addressed messages over intermediating channels.
• Negative Case Analysis — Deliberately hunt the cases that would overturn your account, then revise or scope it.
• Observable Surface Becomes Contract — Every observable behaviour, exposed to enough observers over enough time, becomes a binding dependency regardless of the nominal contract.
• Open-Closed Principle — Harden a stable kernel against modification and route all change through an open extension surface.
• Operationalization — A specification of what is wanted is mechanically lowered into an executable how, under a correctness contract relating the two.
• Refactoring — Change internal structure while preserving observable behavior.
• Supersession — A successor explicitly displaces a predecessor in a role, which the predecessor no longer fills going forward even while it persists for historical reference.
• Wizard Of Oz Prototyping — Validate a planned system cheaply by making its surface convincingly present while a hidden operator supplies the not-yet-built interior.
• Zero Knowledge Proof — Convince a verifier a claim is true while revealing nothing beyond its truth.