Core Concepts

This page only standardizes vocabulary and points to authoritative pages. The capability guides own procedures, runtime state machines, and complete examples.

command payload
  → CommandMessage envelope
  → aggregate decision
  → domain event payloads in a DomainEventStream
  → sourced aggregate state
  → projections / sagas / other processors

Vocabulary Summary

Term	Stable meaning in Wow	Main artifact
Bounded context	A named business-language boundary containing aggregate definitions	@BoundedContext
Aggregate	One consistency boundary identified by context, aggregate name, tenant, and ID	NamedAggregate, AggregateId
Command	An imperative payload requesting a state change	data class/object, @CreateAggregate, @CommandRoute
Command message	Runtime envelope carrying the command plus identity, request, version, headers, and routing metadata	CommandMessage<C>
Command aggregate root	Domain object that checks invariants and returns events	@AggregateRoot, @OnCommand
State aggregate root	State object rebuilt only by sourcing events	@OnSourcing
Domain event	Immutable business-fact payload	data class/object; @Event for explicit metadata
Domain event envelope	Runtime event plus aggregate, command, sequence, revision, and time metadata	DomainEvent<T>
Event stream	Ordered batch of events produced by one aggregate command	DomainEventStream
Event store	Authoritative append/load contract for aggregate event streams	EventStore
Snapshot	Replaceable derived checkpoint used to accelerate aggregate restoration	SnapshotStore
Wait stage	A caller-selected definition of command completion	SENT, PROCESSED, SNAPSHOT, PROJECTED, and others
Projection	Event processor that maintains a read model	@ProjectionProcessor, @OnEvent
Saga	Event processor that coordinates across aggregates by sending later commands	@StatelessSaga, @OnEvent
Event compensation	Observable recording, scheduling, and retry of failed event-processing work	compensation records, RetrySpec

Key Boundaries

• A command handler decides from current state and returns events; only deterministic, side-effect-free sourcing functions change state.
• Event streams appended to EventStore are authoritative history. Snapshots and projections are rebuildable derived data.
• SENT, PROCESSED, SNAPSHOT, and function-scoped downstream stages prove different boundaries and cannot substitute for one another.
• A Processor owns ordinary side effects, a Saga sends cross-aggregate commands, and event compensation retries a failed function. A business reverse action remains an explicit domain command.
• Projection completion does not automatically prove query visibility. Execute the real query when the user-visible result is the contract.

Authoritative Reading Paths

Capability	Authoritative pages
Domain boundaries, history, and restoration	Domain Model, Aggregate and Invariants, Event Sourcing, Event Evolution, Snapshots, Aggregate Lifecycle
Command definition, invocation, and results	Commands, Define Commands, Send Commands, API Client, Completion Semantics, Failures and Idempotency
Command runtime internals	Command Processing Pipeline, Command Wait Runtime, Command Transport and Routing
Event processing and cross-aggregate collaboration	Events and Collaboration, Event Processor, Saga, Event Compensation, Event Dispatch Pipeline
Read models and queries	Projection, Query, Data Access Control