Foundation Pattern

Event Modeling

Event Modeling represents discrete business events that happened at a specific point in time.

Problem

Not every historical fact is a state.

Many business processes are better represented as events: a claim is filed, a payment is received, a contract is changed or a customer status is updated.

Event Modeling captures what happened, when it happened and which entity it affected.

Duplicate eventsIncorrect orderingMissing timestampsState/event confusion

Example

A contract history can be represented as a sequence of events.

Jan 05

Contract created

A new contract is opened for the customer.

Apr 10

Premium changed

The premium is updated after a business change.

Sep 20

Contract cancelled

The contract lifecycle ends with a cancellation event.

entity_id | event_type        | event_time
C-1001    | CONTRACT_CREATED  | 2024-01-05
C-1001    | PREMIUM_CHANGED   | 2024-04-10
C-1001    | CONTRACT_CANCELLED| 2024-09-20

The event stream can later be used to derive state, snapshots or audit history — but only if the events are complete, ordered and correctly interpreted.

Why it happens

Business changes often happen as point-in-time actions.

Events describe transitions, decisions or transactions. They are not valid over an interval by themselves, but they can be used to derive state, snapshots or audit history.

CDC streamsAudit journalsTransactionsStatus changesContract mutationsBusiness process logs

Common modeling approaches

Store one row per business event.

Use event time

Store event_time or effective_at as the business timestamp of the event.

Keep ingestion separate

Do not confuse when the event happened with when it arrived in your platform.

Preserve ordering

Define deterministic ordering within each entity, especially for same-day or same-second events.

Derive state carefully

Only derive states or snapshots after validating that the event stream is complete enough.

Validation checks

Validate the event stream before deriving history.

✓ Detect duplicate events✓ Validate event ordering per entity✓ Check required event types✓ Detect missing or impossible timestamps✓ Validate event-to-state alignment

Why it matters

Events explain how business history changed.

Event Modeling is the foundation for understanding how business changes happened.

Many reporting models eventually need both state and events: state to answer what was true, and events to explain what changed.

Related Patterns

State Modeling State ↔ Event Alignment Bitemporal Modeling Historical Backfill Snapshot Reproducibility

Try it

Explore event-to-state behavior in the Workbench.

Use the Historical Modeling Workbench to reason about event streams, derived states, historical joins and reporting behavior.

Open Historical Modeling Workbench →