An artifact tree — a repository, a directory, a document set — is an interface, and it is read before any file is opened. Names, placement, sort order, prominence, a suffix: these reach a visitor ahead of every sentence, and they are doing work whether or not anyone designed them. The only choice available is deliberate or accidental.
Spent deliberately, affordances do three jobs:
Shaping attention. What wandering lands on is what gets read, so prominence is a budget. Entrypoints and summaries belong front-and-center; archives, machinery and ground truth belong a step removed, reachable on purpose. The polarity runs both ways: burying an entrypoint quietly reclassifies it (a log whose newest page sits two clicks deep reads as an archive, whatever it says), and exposing internals taxes every visitor with a decision they shouldn’t have to make.
Enabling discovery. Structure answers where would X be? before anyone greps. Consistent marks and mirrors make locations predictable — what you read at one path, you file at its counterpart — and predictability compounds: a rule expressible as a path convention is discoverable by every visitor, human or stateless; a rule living only in prose is discoverable by whoever happens to read that prose.
Diagnosis. Affordance inconsistency is a smell to read, not an untidiness to tolerate — the same shape carrying opposite rules, a file whose neighbours are the wrong kind. That reading turned out not to be about affordances at all: the citation graph reports the same class of fault the same way, so it is now DP-016, and this is the tree half of it.
Two disciplines keep the spend honest. Structural beats documentary: a comment saying “GENERATED — do not edit” is read after landing in the wrong place and enforces nothing; a directory name is read before, and a linter can hold it. And where the structure encodes a checkable property, walk it up DP-5’s ladder — the read/write boundary (ADR-021) is this principle’s worked application, and its payoff rung is a lint: a view directory holds only what the generator wrote, so a hand edit there fails with the polarity DP-3 demands.
The sibling claim, from the pilot: SG-DP-18, “the affordance is the contract” — an affordance must not lie; what a control suggests is what the action does, verified from the same inputs. That principle binds affordances to the truth. This one is its complement about reach: affordances are the widest channel an artifact has — spend them, don’t merely avoid falsifying them.