Competency criteria models (authoring/definition layer)

User Story

As a course author, I want a competency's completion requirements stored as an ordered
AND/OR tree of criteria, in order to express a rule like "pass the final and either lab"
rather than a single flat threshold.

Acceptance Criteria

• CompetencyTaxonomy has the taxonomy_overrides_org boolean, default false. The model itself shipped in PR feat: provide openedx_learning djangoapp and CompetencyTaxonomy model #712 without this column.
• CompetencyCriteriaGroup has all required columns: id, parent_id (nullable self-FK), oel_tagging_tag_id, course_id (nullable ForeignKey to openedx_catalog.CourseRun), name, ordering, logic_operator (AND/OR/null).
• openedx_catalog is added to .importlinter's root_packages and placed in the src_layering contract below openedx_learning. Today it appears in neither, so the first openedx_learning to openedx_catalog import would pass unexamined. lint-imports passes with no rule loosened. It is placed as an independent sibling of openedx_content, written openedx_content | openedx_catalog, rather than as a layer of its own above or below it: layers is a strict total order, so a layer of its own would also decide the catalog-to-content direction that src/openedx_catalog/ARCHITECTURE.md records as undecided. [BE] Implement CBE core data models (CompetencyTaxonomy, criteria, learner status) #613's wording says only "below openedx_learning" and needs the same clarification.
• logic_operator accepts AND, OR or null, per ADR-0002 Decision 2, and nothing at the data layer constrains it by child count. That rule cannot hold here: a group's children need its primary key, so the group's own clean() always sees zero children, and adding a child later calls the child's clean(), never the parent's. Whatever rule governs null is enforced in the authoring API, when a tree is saved as a unit.
• No UniqueConstraint on (parent_id, ordering) is added. ADR-0002 requires none, and it would settle only half the ordering question: a group's children are both child groups and leaf CompetencyCriteria rows, and the leaf model has no ordering column at all, so sibling order among leaves would stay undefined while looking solved.
• CompetencyRuleProfile has every column from ADR-0002 Decision 3: id, organization_id, course_id, competency_taxonomy_id, scope_code, rule_type, rule_payload, archived. rule_payload is a validated JSON field with shape enforced per rule_type.
• scope_code is a generated, never-null column in the format "org:X,course:Y,taxonomy:Z", non-null for the system-default row where all three scope columns are null, with a unique constraint on scope_code alone.
• The scope_code migration is applied against MySQL, not only the SQLite used for local runs. ADR-0002 Rejected Alternative 6 records that the obvious substitute, a conditional UniqueConstraint over the three nullable columns, compiles to a partial index that MySQL does not support: Django emits a models.W036 warning, skips the constraint, and SQLite supports partial indexes so local tests stay green. A passing local suite is not evidence here.
• A check constraint enforces that at most one of organization_id, course_id and competency_taxonomy_id is non-null, with a test for each rejected two-column combination.
• A data migration seeds the single system-default CompetencyRuleProfile, the row where all three scope fields are null. It is seeded with archived false, rule_type "Grade", and rule_payload {"op": "gte", "value": 0.8, "scale": "percent"}, which means "a grade of 80% or higher". Note that value is a fraction between 0.0 and 1.0, not a number out of 100 (ADR-0002 Decision 3), so 80% is written 0.8. This is the rule every competency criterion falls back to when nothing more specific applies, so a deployment that installs this app and adds no profiles of its own gets an 80% threshold.
• CompetencyRuleProfile scope fields are immutable after creation; editing a profile may change rule_type and rule_payload only, so that criteria already resolved to a profile are never silently re-scoped.
• The leaf model has all required columns, including nullable competency_rule_profile_id, rule_type_override and rule_payload_override, with the same validation contract. Its class name is CompetencyCriterion, singular, matching ADR-0002 Decision 4, which calls one leaf a criterion. No Meta.db_table override is added, so the table is openedx_learning_competencycriteria; see "The three criteria models" above for why. [BE] Implement CBE core data models (CompetencyTaxonomy, criteria, learner status) #613 still asks for Meta.db_table = "CompetencyCriteria" and needs the same correction.
• A check constraint enforces ADR-0002 Decision 4's invariant: either competency_rule_profile_id is set and both override fields are null, or competency_rule_profile_id is null and both override fields are set. Never both, never neither. A test covers each of the two invalid states.
• Nothing resolves competency_rule_profile_id at read time. ADR-0002 Decision 4 assigns it at four named write events and stores the result, and says the FK is never re-resolved dynamically at evaluation time. The assignment computation itself is API-layer work and is out of scope here.
• rule_payload and rule_payload_override shape validation is enforced in clean(), reached via full_clean(); a test must call full_clean() with an invalid payload and assert ValidationError is raised. clean() is a convenience for the admin and for tests, not an enforcement layer: Django's ModelForm calls full_clean(), but DRF's ModelSerializer never does, and neither does QuerySet.update() or bulk_create().
• The indexes from ADR-0002 Decision 5 that belong to these models are present: 1 (CompetencyCriteriaGroup(oel_tagging_tag_id, course_id)), 2 (CompetencyCriteriaGroup(parent_id)), 4 (CompetencyCriteria(oel_tagging_objecttag_id)), 5 (CompetencyCriteria(competency_criteria_group_id)) and 9 (CompetencyRuleProfile(scope_code)). Index 9 must be unique; a plain index there fails this criterion. Index 3, oel_tagging_objecttag(object_id), is already satisfied by the existing db_index=True on ObjectTag.object_id (src/openedx_tagging/models/base.py), so no work is required for it here. Indexes 6, 7, 8 and 10 come from Mastery status lookup + learner progress models #642, which verifies all ten end to end.
• CompetencyCriteriaGroup, CompetencyCriterion and CompetencyRuleProfile each carry a uuid external identifier alongside the internal id, following this repo's identifier convention, so that the REST APIs and events built on them are never forced to expose an integer primary key.
• The models added here are registered in .annotation_safe_list.yml (or annotated inline) as .. no_pii:, including the three models django-simple-history generates: HistoricalCompetencyCriteriaGroup, HistoricalCompetencyCriterion and HistoricalCompetencyRuleProfile. Those are real Django models and the annotation scan counts them; this is the first use of django-simple-history anywhere in src/, so nothing in this repo has hit that before. Mastery status lookup + learner progress models #642, as the last ticket to merge, carries the make pii_check 100% coverage gate for the feature as a whole.
• django-simple-history (HistoricalRecords()) is applied to CompetencyCriteriaGroup, CompetencyCriterion and CompetencyRuleProfile.
• django-simple-history is not applied to oel_tagging_tag, oel_tagging_taxonomy, or CompetencyTaxonomy.
• Migrations are present and apply cleanly on top of CBE app foundation + CompetencyTaxonomy model #640's migration.
• No column exists on the models added here beyond those in ADR-0002 Decisions 1 through 4, the constraints, identifiers and timestamps this ticket lists, and the columns django-simple-history generates. One exception, listed again under Deletions below: the archived column that the 2026-09-01 amendment added to Decisions 2 and 4 is not added here, because [BE] Add archived field to CompetencyCriteriaGroup and CompetencyCriterion #716 owns it.
• All FK relationships match the ADR definitions exactly, targets included: course_id points at openedx_catalog.CourseRun.

Deletions

• The four foreign keys that carry Django's collector down the criteria tree are CASCADE: CompetencyCriteriaGroup.tag, CompetencyCriteriaGroup.parent, CompetencyCriterion.group and CompetencyCriterion.object_tag. These are what make ADR-0002 Decision 7's delete protection work, because the PROTECT that blocks a delete lives on Mastery status lookup + learner progress models #642's Student*Status foreign keys, two of which point at rows one and two levels below the tag, and Django reaches them only by walking down foreign keys marked CASCADE.
• CompetencyRuleProfile.competency_taxonomy is CASCADE, not PROTECT, so a rule profile is never the reason a taxonomy delete fails. Blocking a taxonomy delete when learner data is connected to it is an application-layer requirement, not a database constraint; see the requirement above and [BE] Implement CBE core data models (CompetencyTaxonomy, criteria, learner status) #613.
• The other four are PROTECT: CompetencyCriterion.rule_profile, CompetencyCriteriaGroup.course, CompetencyRuleProfile.course and CompetencyRuleProfile.organization. No TODO comment is attached to any of the nine; all nine values are final.
• Only the cascade half of each delete case is tested here. Every matching ProtectedError case belongs to Mastery status lookup + learner progress models #642, because asserting one requires a Student*Status row and Mastery status lookup + learner progress models #642 is the ticket that creates those three tables. This ticket merges first, so the rows those assertions need do not exist yet.
• Deleting an oel_tagging_tag succeeds and removes the whole criteria tree beneath it: every CompetencyCriteriaGroup for that tag, every descendant group, and every CompetencyCriterion under any of them.
• Deleting a CompetencyCriteriaGroup at depth succeeds and removes the target, every descendant group, and every criterion under any of them.
• Deleting an oel_tagging_objecttag succeeds and cascades its criteria away, leaving the parent group behind.
• Deleting an oel_tagging_taxonomy succeeds and removes the criteria trees of every tag beneath it. Tag.taxonomy is already CASCADE in openedx_tagging, which is what makes the tag case above hold transitively from the taxonomy.
• No delete() override, no archive-versus-delete branch, and no deletion-lock field lands in this ticket. The cascade is declared on the foreign keys and nothing here implements deletion behavior in code. [Arch] Implementation approach for competency data delete/edit guardrails #655's approved design enforces archive-versus-delete entirely at the application layer, driven by a persisted lock flag on oel_tagging_objecttag, which changes openedx_tagging as well as CBE.
• CompetencyRuleProfile.archived exists as a column defaulting to false, per the ADR-0002 Decision 3 criterion above. Nothing in this ticket enforces that a profile is only archived and never deleted. [Arch] Implementation approach for competency data delete/edit guardrails #655 resolves that differently rather than deferring it: the model gets no DELETE endpoint at all, and only the single system-default row exists in MVP.
• No archived column is added to CompetencyCriteriaGroup or CompetencyCriterion. ADR-0002 Decisions 2 and 4 now list one on each, added by the 2026-09-01 amendment for [Arch] Implementation approach for competency data delete/edit guardrails #655, but [BE] Add archived field to CompetencyCriteriaGroup and CompetencyCriterion #716 owns landing it. Read the "no column beyond ADR-0002 Decisions 1 through 4" criterion above with that carve-out.

Description

This is one of three tickets implementing #613's model layer, and the first of the three
to merge. Every criterion above is one of #613's, or one of #613's narrowed to this
ticket's models. Nothing here is additional to the parent.

Open Questions

• Once taxonomy-scoped CompetencyRuleProfile rows exist, does CompetencyCriterion.rule_profile
  still want PROTECT? Owner: whoever designs the application-layer guardrail described in
  Technical Details. Not settled here; see [BE] Implement CBE core data models (CompetencyTaxonomy, criteria, learner status) #613.