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| <mainDescription><p> |
| To fully understand the system's purpose, you must know who the system is for, that is: Who will use the system? The |
| answer to this question is: the Actors. |
| </p> |
| <p> |
| An Actor is a role that a person or external system plays&nbsp;when interacting with the system.&nbsp; Instances of an |
| Actor can be an individual or an external system, however each Actor&nbsp;provides a |
| unique&nbsp;and&nbsp;important&nbsp;perspective on the system that is shared by every instance of the Actor. |
| </p> |
| <p> |
| This difference between an actor and an instance of an actor is illustrated below.&nbsp;&nbsp;Figure 1 shows a case in |
| which Ivar and Mark are operators of a recycling machine. When they are using the machine in this capacity, each is |
| represented by an instance of the actor called Operator that expects certain functionality of the system (Print Daily |
| Reports in this example). |
| </p> |
| <p> |
| <img height="322" alt="" src="./resources/md_acto2.gif" width="396" />&nbsp; |
| </p> |
| <blockquote dir="ltr" style="MARGIN-RIGHT: 0px"> |
| <p> |
| <strong>Figure 1:&nbsp;Example Actor with multiple instances</strong>&nbsp; |
| </p> |
| </blockquote> |
| <p> |
| Conversely, the same user can act as several actors (that is, the same person can take on different roles). In Figure |
| 2, Charlie uses the Depot-Handling System primarily as Depot Manager, but sometimes he also uses the Depot-Handling |
| System as an ordinary Depot Staff member. Each of these actors expects different functionality of the system. |
| </p> |
| <p> |
| <img height="139" alt="" src="./resources/md_acto3.gif" width="367" /> |
| </p> |
| <blockquote dir="ltr" style="MARGIN-RIGHT: 0px"> |
| <p> |
| <strong>Figure 2: Example of user playing different roles</strong><br /> |
| </p> |
| </blockquote> |
| <p> |
| Actors help you to identify external interfaces and to determine the scope the system (what is in the system, vs. what |
| is outside the system boundary).&nbsp; Each&nbsp;Actor has associated use cases which describe what that |
| particular&nbsp;actor expects of the system.&nbsp; It will be very difficult, if not impossible,&nbsp;to assess the |
| completeness of the set of Use Cases without the context provided by the associated Actors. Furthermore, missing an |
| actor may result in&nbsp;missing important stakeholder perspectives, resulting&nbsp;in a solution that does not meet |
| all&nbsp;stakeholder needs. |
| </p> |
| <p> |
| Hence, identifying the Actors for the system&nbsp;should be done early in the lifecycle.&nbsp;&nbsp;Actors are |
| captured, including their names, brief descriptions, and relationships to use cases,&nbsp;in the <a |
| class="elementLinkWithType" href="./../../../openup_basic/workproducts/uc_model,_W2SgEDR5EdutE_HNDTJk5Q.html" |
| guid="_W2SgEDR5EdutE_HNDTJk5Q">Artifact: Use-Case Model</a>. |
| </p></mainDescription> |
| </org.eclipse.epf.uma:ContentDescription> |