Supported

Retention, deletion, and purpose

Contract

Knowledge	Policy	At evaluation time	Result
Session transcript	30-day TTL	31 days old	Expire and remove from retrieval
Derived preference	Depends on transcript	Parent deleted	Tombstone and invalidate projection
Compliance evidence	Seven-year retention	User requests ordinary deletion	Hold. Record policy reason
Support address	Purpose: order fulfillment	Marketing retrieval	Deny for incompatible purpose

How it works

Retention and freshness produce independent decisions. plan_retention emits delete actions for expired records, hold actions for expired held records, and invalidations for reachable derivatives. Each action contains the record ID, kind, and reason. The host persists its own tombstones and event times, removes content from reads, and applies storage retention policy.

Plan deletion through derivation edges

from datetime import datetime, timezone

from mari_components.governance import RetentionPolicy, plan_retention

plan = plan_retention(
    records=records,
    dependencies=dependencies,
    now=datetime.now(timezone.utc),
    policy=RetentionPolicy(
        default_ttl_days=30,
    ),
)

for action in plan.actions:
    store.apply_retention(action)

Mari produces a plan. The storage adapter performs physical deletion. Database-specific erasure and legal policy stay outside the core. Mari’s dependency records keep that part testable.

dependencies maps each parent record ID to its derived child IDs. A held child can still receive an invalidation when its parent expires. Invalidation marks derived work unusable and physical preservation remains the host’s job. Repeated calls return deterministic actions. Persist applied-action identity in the host to make effects idempotent.

Purpose checks use evaluate_purpose(record, requested_purpose=...) and the record’s purposes tuple. Apply that decision before retrieval. RetentionPolicy.allowed_purposes is currently stored configuration and is independent of the expiration planner’s decisions.

Measures

Invariant	Expected result
Expired artifact retrieval	Zero returned content
Dependency cascade	Every reachable derivative invalidated
Legal hold	Held expired record receives HOLD in place of DELETE
Purpose mismatch	Access denied before ranking
Repeated planning	Same actions for the same inputs. Host deduplicates effects

Papers and implementations

Machine unlearning surveySISA trainingPortable Memory tombstonesGDPR Article 5

Model-weight unlearning is outside Mari. The relevant mechanism is deletion from stores, indexes, bundles, and derived knowledge.