Constraints

A constraint records a violation as data instead of failing silently. The frame#record rule below fires whenever a person works at a company while hasJob is false.

// Violation recorded as an ordinary derivable fact.
frame#record[frame#tuple(violation#job_conflict, ?X) -> true] <- ?X : Person AND ?X[worksAt -> ?C] AND ?C : Company AND ?X[hasJob -> false].

expect true: frame#record[frame#tuple(violation#job_conflict, rob) -> true].