Describe a symbolic foreign-key relation — key

A key relation does not duplicate a mapping. It declares that one scalar column on an observation, feature, or entity table references the stable IDs of one entity frame.

Usage

key_relation(
  key,
  target = NULL,
  source = "observation",
  allow_missing = FALSE,
  metadata = list()
)

Arguments

key: Foreign-key column on the source domain.
target: Target entity name. When NULL, frame validation infers the unique entity whose primary key has the same name as key.
source: Source domain: "observation", "feature", an entity name, or an explicit "entity:<name>" domain.
allow_missing: Whether missing foreign-key values are permitted.
metadata: Additional serializable metadata.

Value

A serializable key_relation descriptor.

Examples

rel <- key_relation("stimulus_id", target = "stimulus", source = "observation")
rel$key
#> [1] "stimulus_id"