Crate pai_drift 

PAI Drift Correlation Engine (Component #4)

Per PHASE1-TZ-001 Section 7 / P0-1 Section 7.4.

Cross-dimension drift correlation across 7 monitored dimensions:

Dimension	Source	Weight
Identity changes	Consent / Delegation mutations	1.0
Objective adjustments	Objective Registry mutations	1.5
Personalization modifications	Identity Layer changes	1.0
Classification rule updates	Tier reassignments	2.0
Upgrade events	Governance logic changes	2.0
Upgrade frequency	Count per rolling window	1.0
Governance modifications	Enforcement scope changes	2.5

Architecture

• Time-based rolling window: events older than window_secs are expired on every record() call.
• Per-dimension score = sum of deltas within the window.
• Composite score = sum(weight_i * dim_score_i).
• When composite >= threshold, record() returns true and DriftReport::breached is set — the caller MUST activate Conservative Mode.
• Thresholds are immutable once the engine is constructed (absent Amendment — DFT-I5).

Invariants

• DFT-I1: Dimension scores are monotonically non-decreasing within a window until events expire.
• DFT-I2: Window eviction is time-based (old events expire).
• DFT-I3: Composite score is deterministic for the same event sequence.
• DFT-I4: Threshold breach always signals Conservative Mode.
• DFT-I5: Thresholds are immutable after construction.

Structs

DriftEngine

Cross-dimension drift correlation engine.

DriftReport

Snapshot of the engine’s current drift state.

DriftThresholds

Drift thresholds. Immutable once constructed (absent Amendment).

Enums

DriftDimension

The 7 drift dimensions per PHASE1-TZ-001 Section 7.2.

Constants

DIMENSION_COUNT

Number of monitored drift dimensions.