How to Identify Business Actors?

In creating use case and use case diagrams, actors are identified first. Why? Because by focusing on the actors, you can concentrate on how the system will be used and not how it will be built. Focusing on the actors helps to refine and further define the scope and boundaries of the system.

So, where do you look for potential actors? The following references are excellent sources:

• Your context diagram that identifies the scope and boundaries of the system.
• Existing forms and reports and other documents. 

When you are deciding for your actors, you might want to ask yourselves the following questions:

• Who or what provides inputs to the system?
• Who or what receives outputs from the system?
• Are interfaces required to other systems?
• Are there any events that are automatically triggered at a predetermined time?
• Who will maintain information in the system?

Reference:
System Analysis and Design for the Global Enterprise
by: Bentley and Whitten