![]() So an external system can also be an implementation detail left out of the UC diagram. it would not add any observable result of value for the stakeholders of the system under consideration). The diagram is used to model the system/subsystem of an application. But this one should in principle not be considered as an actor, if the DBMS is a design decision that is not relevant for the use case (i.e. Use case diagrams consists of actors, use cases and their relationships. A use case describes a sequence of actions that provide something of measurable value to an actor. Your Computer actor is in fact internal system therefore should not be modeled as an actor. ![]() So IMHO, this secondary actor should better be called Cardholder's bank instead of SWIFT for a higher accuracy and a more general solution.įor the sake of completeness, let's take another example: a third party DBMS could also be considered as an external system. An actor is a person, organization, or external system that plays a role in one or more interactions with your system. In reality, SWIFT is only a network used to reach the cardholder's bank. This interaction would most probably be mentioned in the use case requirements (regardless of how the ATM software would be implemented). As the following figure illustrates, an extend relationship is displayed in the diagram editor as a dashed line with an open arrowhead pointing from the extension use case to the base use case. In plain text this means that in your example, SWIFT could be a good candidate for an actor: the ATM has to interact with SWIFT to ensure the money is withdrawn from the holder's bank. An actor is behaviored classifier which specifies a role played by an external entity that interacts with the subject (e.g., by exchanging signals and data), a human user of the designed system, some other system or hardware using services of the subject. In UML modeling, you can use an extend relationship to specify that one use case (extension) extends the behavior of another use case (base). Specification of its associated UseCases. Instead a particular role of some entity that is relevant to the ![]() To quote a (non binding) note of the UML standard:Īn Actor does not necessarily represent a specific physical entity but 4.3K views 2 years ago Use case diagram in software engineering. If the actor is on the right, it means that the actor is a secondary one: he participates. In the Unified Modeling Language (UML), a use case diagram can summarize the details of your systems users (also known as actors) and their interactions with the system. The usage is: if the actor is on the left, it means thats a 'primary actor', the actor who activates the use case. Please see image extracted from the norm. Yes, actors CAN be human users or external systems.īut not all the external systems SHOULD be actors. This is an association, in the norm, association between actor and use has no direction. H lô h lô, Ông dev âyTrong phn này mình s nói v Use Case Diagram.Tóm tt:- Trong UML có 4 i tng: + System + Actor + Use Case + Relationship- S. ![]()
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