Editing Use case (section)

== Actors ==
{{Main|Actor (UML)}}

A use case defines the interactions between external actors and the system under consideration to accomplish a goal. Actors must be able to make decisions, but need not be human: "An actor might be a person, a company or organization, a computer program, or a computer system—hardware, software, or both."<ref name=Cockburn53>Cockburn, 2001. Page 53.</ref> Actors are always [[Project stakeholder|stakeholders]], but not all stakeholders are actors, since they may "never interact directly with the system, even though they have the right to care how the system behaves."<ref name=Cockburn53/> For example, "the owners of the system, the company's board of directors, and regulatory bodies such as the Internal Revenue Service and the Department of Insurance" could all be stakeholders but are unlikely to be actors.<ref name=Cockburn53/>

Similarly, a person using a system may be represented as a different actor because of playing different roles. For example, user "Joe" could be playing the role of a Customer when using an Automated Teller Machine to withdraw cash from his own account or playing the role of a Bank Teller when using the system to restock the cash drawer on behalf of the bank.

Actors are often working on behalf of someone else. Cockburn writes that "These days I write 'sales rep for the customer' or 'clerk for the marketing department' to capture that the user of the system is acting for someone else." This tells the project that the "user interface and security clearances" should be designed for the sales rep and clerk, but that the customer and marketing department are the roles concerned about the results.<ref name=Cockburn55>Cockburn, 2001. Page 55.</ref>

A stakeholder may play both an active and an inactive role: for example, a Consumer is both a "mass-market purchaser" (not interacting with the system) and a User (an actor, actively interacting with the purchased product).<ref name=AB39>Alexander and Beus-Dukic, 2009. Page 39.</ref> In turn, a User is both a "normal operator" (an actor using the system for its intended purpose) and a "functional beneficiary" (a stakeholder who benefits from the use of the system).<ref name=AB39/> For example, when user "Joe" withdraws cash from his account, he is operating the Automated Teller Machine and obtaining a result on his own behalf.

Cockburn advises looking for actors among the stakeholders of a system, the primary and supporting (secondary) actors of a use case, the system under design (SuD) itself, and finally among the "internal actors", namely the components of the system under design.<ref name=Cockburn53/>