What are an actor, an interaction and a component in the CSA notation?

An actor triggers an action, and can be a person or any cyber device; an interaction is an action triggered by an actor on a component, drawn as an arrow from actor to component; a component is a part belonging to a system, which can itself be any cyber device or subsystem.

* A person or a service can trigger the action; the arrow always runs from the actor to the component. *

• Actor: the trigger of an action. Besides people, this can be any kind of cyber device: an IT system, IT service, OT system, machine, smartphone, application, resource or IoT device. Actors that are not people are called non-human identities (NHI).
• Interaction: the action an actor triggers on a component. The arrow always points from the actor to the component.
• Component: a part of a system. It can again be any cyber device or a whole subsystem.

A service can be an actor in one interaction and a component in another, which is typical of modern systems where services call each other.

Go deeper:

• Actor (UML) — Wikipedia — the same idea in UML: an actor is a role played by a user or another system, and one entity can play several roles.
• OWASP Non-Human Identities Top 10 — 2025 — why non-human actors need their own security attention: service accounts, keys and tokens.