Glossary

This page defines terms used across the LiteBus v6 documentation. Each entry links to the page that explains it in depth.

Core Concepts

Term	Definition
Mediator	The in-process component that routes a message to its handlers. LiteBus exposes typed mediators (`ICommandMediator`, `IQueryMediator`, `IEventMediator`) over a shared `IMessageMediator`. See Architecture.
Command	A message expressing an intention to change state. Resolves to exactly one main handler. See Command Module.
Query	A message that reads state and returns a result. Resolves to exactly one main handler. See Query Module.
Event	A message reporting a fact. Broadcasts to every matching handler, or none. See Event Module.
Handler	A class that processes a message. The single class that does the work is the main handler.

Term	Definition
Pipeline	Pre-handlers, main handler, post-handlers, and error-handlers for one message. See The Handler Pipeline.
Pre-handler	Runs before the main handler.
Post-handler	Runs after the main handler.
Error-handler	Runs when a stage throws.
Execution context	Ambient per-mediation state (`AsyncLocal`). See Execution Context.

LiteBus keeps domain-specific names instead of one generic "store" verb:

Term	API	Meaning
Accept	`IInbox.AcceptAsync`	Store a command-shaped message for later execution by the inbox processor.
Enqueue	`IOutbox.EnqueueAsync`	Store an event-shaped message for later publication by the outbox processor.
Schedule	`MessageVisibility` on `InboxAcceptMetadata` / `OutboxEnqueueMetadata`	Accept or enqueue with a future `VisibleAfter` timestamp.

Term	Definition
Inbox	Storage that accepts messages through `IInbox.AcceptAsync` for later execution. See Inbox.
Outbox	Storage that records messages through `IOutbox.EnqueueAsync` for later publication. See Outbox.
Stable contract	Persisted message identity: name + integer version. See Architecture Decisions.
Lease	Temporary row ownership so concurrent workers do not process the same envelope twice.
Dispatcher	`IInboxDispatcher` or `IOutboxDispatcher`; executes or publishes a leased envelope.
Processor	`PipelinedInboxProcessor` or `PipelinedOutboxProcessor`; leases rows and invokes dispatchers.
At-least-once	Messages may be delivered more than once; handlers must be idempotent. See Reliable Messaging.
Dead-letter	Terminal state after retry exhaustion.

Term	Definition
`ILiteBusBuilder`	Package-neutral `Modules` entry during `AddLiteBus`; installed packages add normal `Add*` feature extensions.
`Use*` extension	Nested registration on `InboxModuleBuilder` / `OutboxModuleBuilder` (storage, dispatch, ingress). Each maps to one NuGet package. See Dependency Graph.
Manifest	`LiteBusHostManifest` listing `IStartupTask`, `IBackgroundService`, and `IDiagnosticCheck` types. See Hosted services.
`UseInProcessDispatch`	Nested inbox builder extension registering `LiteBus.Inbox.Dispatch.InProcess`; replays leased envelopes through `ICommandMediator`. See Inbox.
`UseInProcessDispatch`	Nested outbox builder extension registering `LiteBus.Outbox.Dispatch.InProcess`; publishes leased envelopes through `IEventMediator`. See Outbox.

Term	Definition
Schema version	Physical table contract recorded per component. Inbox and outbox are version 3; saga is version 2. Ordered migrations cover older v6 tables, not v5 shapes.
Create script	`GetCreateScript()` renders current-version DDL for a new table. See PostgreSQL schema management.
`EnsureAsync` / `ValidateAsync`	Opt-in host bootstrap or validate-only startup for PostgreSQL stores.

Term	Definition
At-least-once	Processors and brokers may deliver the same message more than once. Handlers must be idempotent. See Reliable messaging.
Exactly-once effect	Application responsibility: idempotency keys, deduplication, and handler design; not a broker guarantee.
Idempotency key	`InboxAcceptMetadata.Idempotency` / `OutboxEnqueueMetadata.Idempotency` for store-level deduplication on accept/enqueue.

See Migration Guides for historical upgrades, or Migration Guide v6 for greenfield adoption.