# Tachograph DB / file-session runtime parity

The runtime pipeline treats direct tachograph file-session events and events loaded from the tachograph database as two representations of the same tachograph facts.

## Canonical semantic boundary

`RuntimeTachographEventSemantics` normalizes representation-only differences without modifying the original event:

- file-session and DB source systems are exposed as `TACHOGRAPH`;
- extraction codes are read from DB raw metadata or inferred from source kind and event domain;
- `PLACE START` and `PLACE BEGIN` share the semantic lifecycle `BEGIN` for mixing.

The raw lifecycle, source package, payload, and external source event ID remain unchanged for audit and provenance.

## Runtime aggregation

`RuntimeEventAggregationService` is shared by:

- `TachographFileSessionRuntimeEventLoader`;
- `TachographDbRuntimeEventLoader`;
- `UnifiedRuntimeEventAssemblyService`.

Aggregation removes:

- repeated reads of the same source record;
- duplicate serialized representations of the same extraction observation.

It deliberately preserves evidence pairs that are resolved downstream:

- `CARD_ACTIVITY` / `VU_ACTIVITY`;
- card/VU support evidence;
- `CARD_VEHICLES_USED` / `IW_CYCLE`.

The first two are handled by `RuntimeEventMixingService`. Vehicle usage remains source-distinct until interval-level reconciliation.

## Regression coverage

`RuntimeTachographRepresentationParityTest` verifies equal source profiles and mixing outcomes for DB and file-session representations. `RuntimeEventAggregationServiceTest` verifies that technical duplicates are reduced while card/VU and CVU/IW evidence remains available to later modules.