F.6:12 - Rationale

The direct relation is needed because assignment and Work have different occurrence identities. performedUnderAssignment is an additional world-side fact, not a field stored inside either participant. A separate assertion can say that the assignment obtains, the Work occurred, or their attribution relation obtains.

Using the family ValueKind in F.6 does not license a family-wide assignment signature. It lets F.6 project the actual holder from each occurrence through its species-declared holder slot while preserving any commission, position, locus, or other real participant. Creating a generic assignment for F.6 would duplicate the episode and weaken attribution identity.

Making a log, status, decision, or evidence item a participant would confuse attribution with knowledge of attribution. Creating RoleEnactmentFact would duplicate Work and the same relation. Treating a matching holder and temporal coverage as enough would instead attribute one Work to every overlapping assignment held by its performer. The two-participant relation avoids both errors: the case fact linking Work to assignment is checked separately, while assertions and evidence can change without rewriting the Work, assignment, or their link.