Mapping

A mapping is a derivation rooted in a source observation. For example, a mapping from a shipment notice to shipment lines computes zero or more target values per notice. It can discard source distinctions, such as the spelling of a unit. A query instead takes input collections and parameters and defines named results.

An inverse lookup may find several notices compatible with a line. That is different from reconstructing the original notice. A bidirectional transformation must declare its inverse and the laws it satisfies; codecs make those promises explicit at representation boundaries.

Formal relations

• refines: Relation — Computes the corresponding target values from each source observation.