Defines a partition boundary finer than tenant level — an engagement, a matter, a project — within which content and authorship are scoped, independent of role or department.
Low; one per active engagement or walled project
Retained for the life of the engagement plus a compliance-driven tail
Only the control-bearing entities were modelled for lifecycle. Defensible as a starting point, but it does leave the entity model uneven, and this is incompleteness rather than a finding.