Actor describes user role or systems that interact with the software.
An actor is a classifier that represents a group of users who interact with the system.
Actors can be used to classify:
Business Requirements
Software Requirements
Types of Actors in Almware
User. A user who interacts with the software. E.g. visitor, an authorised user or an administrator. If software implements static roles, it can be used to classify functional requirements by role.
Internal System. An internal system actor, such as a timer.
External system. An external system that interacts with the software, often for integration purposes.