defprotocol

(defprotocol Name docstring? (method [target & args] docstring?) ...)

Declares a protocol: a method-table global plus one dispatcher per method over the target's tag (the multimethod shape without the hierarchy search). The name answers its method table. A call dispatches on the target's exact tag, then the Object row; a miss with no Object row signals, like the oracle. Each method takes one parameter vector -- several arities stay refused.

With :extend-via-metadata true a value also implements a method through its metadata (with-meta), keyed by the namespace-qualified method symbol (`area or 'user/area). The order is the oracle's: an implementation in a defrecord/deftype/reify body, then the metadata, then the extend-type rows and Object. satisfies? does not look at metadata, like the oracle.