One Entry Point per Module for Business Logic

Goal

Every business-logic entry point must be a separate module. Do not group multiple entry points together in the same class, object, or file because they operate on the same domain entity type.

A module here means the unit of code organization provided by the language: a file, a single-class file, a single-object file, or equivalent. Each entry point gets its own.

What Counts as In Scope

Apply this skill to code that does one or more of these things:

• defines multiple business-logic entry points in a single class, object, or file
• groups command handlers, query handlers, use cases, or application services by domain entity type into a shared container
• introduces a service class or facade that bundles several business operations as methods on one object
• organizes business-logic entry points by entity rather than by operation

The Rule