What are the best methods for identifying actors in a use case diagram?

1 Define actors

Actors are the roles that interact with the system, either directly or indirectly. They can be human users, such as customers, employees, or managers, or they can be other systems, such as databases, applications, or devices. Actors are not specific individuals or instances, but rather general types or categories of users or systems. To define actors, you need to ask yourself who or what initiates, participates in, or benefits from the use cases of the system.

2 Use external perspective

One way to identify actors is to use an external perspective, that is, to look at the system from the outside and see who or what interacts with it. This can help you avoid including internal details or components of the system that are not relevant for the use case diagram. For example, if you are modeling a banking system, you might identify actors such as customers, tellers, managers, ATMs, and other banks. You would not include actors such as accounts, transactions, or security systems, as they are part of the internal logic of the system.

3 Use stakeholder analysis

Another way to identify actors is to use stakeholder analysis, that is, to identify and analyze the interests, needs, and expectations of the people or organizations that are affected by or have influence over the system. This can help you discover actors that might not be obvious from the external perspective, but are important for the success of the system. For example, if you are modeling a health care system, you might identify actors such as patients, doctors, nurses, pharmacists, and insurance companies. You might also include actors such as regulators, auditors, or researchers, as they have a stake in the quality, compliance, or performance of the system.

4 Use personas

A third way to identify actors is to use personas, that is, to create fictional characters that represent the typical or ideal users of the system. Personas can help you understand the goals, motivations, behaviors, and preferences of the actors, and make them more realistic and relatable. To create personas, you need to collect and analyze data from user research, interviews, surveys, or observations. For example, if you are modeling a travel booking system, you might create personas such as Alice, a frequent flyer who values convenience and flexibility, or Bob, a budget traveler who looks for the best deals and discounts.

5 Validate actors

Once you have identified the actors in your use case diagram, you need to validate them to ensure accuracy, completeness, and consistency. This can be done by checking if each actor has a clear and meaningful name that reflects its role or function, and by making sure each actor has at least one use case associated with it. Additionally, there should be no redundant, irrelevant, or ambiguous actors or use cases. Conflicts or contradictions between the actors or use cases should also be avoided. To further validate your actors, you can review them with your stakeholders, users, or experts and seek their feedback and suggestions.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?