# Business Interface

You inject `CommandBus` into a controller. Three controllers later, every call site has the magic-string `'ticket.create'` and a `new CreateTicket(...)`. The bus signature is `mixed → mixed`. There's no single place that documents what your domain can do, no IDE help, and refactoring the `CreateTicket` class is a search-and-replace across the codebase.

A **Business Interface** is your domain's typed API: `interface TicketApi { public function create(CreateTicket $cmd): TicketId; public function close(#[Identifier] string $id): void; }`. Ecotone delivers the implementation. Your controllers, console commands, and subscribers all depend on `TicketApi` — and onboarding a new developer becomes a one-file question: "what can the Ticket module do?".

This works for sending commands, executing queries, and operating on databases — keeping your application code focused on intent rather than wiring.

{% content-ref url="/pages/pQmOc5Wucm8dkY9ZQaej" %}
[Introduction](/modelling/command-handling/business-interface/introduction.md)
{% endcontent-ref %}

{% content-ref url="/pages/1ZR8RZrEnX447XWYz39m" %}
[Database Business Interface](/modelling/command-handling/business-interface/working-with-database.md)
{% endcontent-ref %}


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