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| <mainDescription><h3>
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| Explanation
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| </h3>
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| <p>
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| To fully understand the system's purpose, you must know who the system is for, that is: Who will use the system? The
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| answer to this question is: the Actors.
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| </p>
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| <p>
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| An Actor is a role that a person or external system plays&nbsp;when interacting with the system.&nbsp; Instances of an
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| Actor can be an individual or an external system, however each Actor&nbsp;provides a
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| unique&nbsp;and&nbsp;important&nbsp;perspective on the system that is shared by every instance of the Actor.
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| </p>
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| <p>
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| This difference between an actor and an instance of an actor is illustrated below.&nbsp;&nbsp;Figure 1 shows a case in
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| which Ivar and Mark are operators of a recycling machine. When they are using the machine in this capacity, each is
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| represented by an instance of the actor called Operator that expects certain functionality of the system (Print Daily
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| Reports in this example).
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| </p>
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| <p>
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| <img height="322" alt="" src="./resources/md_acto2.gif" width="396" />&nbsp;
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| </p>
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| <blockquote dir="ltr" style="MARGIN-RIGHT: 0px">
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| <p>
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| <strong>Figure 1:&nbsp;Example Actor with multiple instances</strong>&nbsp;
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| </p>
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| </blockquote>
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| <p>
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| Conversely, the same user can act as several actors (that is, the same person can take on different roles). In Figure
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| 2, Charlie uses the Depot-Handling System primarily as Depot Manager, but sometimes he also uses the Depot-Handling
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| System as an ordinary Depot Staff member. Each of these actors expects different functionality of the system.
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| </p>
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| <p>
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| <img height="139" alt="" src="./resources/md_acto3.gif" width="367" />
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| </p>
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| <blockquote dir="ltr" style="MARGIN-RIGHT: 0px">
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| <p>
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| <strong>Figure 2: Example of user playing different roles</strong><br />
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| </p>
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| </blockquote>
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| <p>
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| Actors help you to identify external interfaces and to determine the scope the system (what is in the system, vs. what
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| is outside the system boundary).&nbsp; Each&nbsp;Actor has associated use cases which describe what that
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| particular&nbsp;actor expects of the system.&nbsp; It will be very difficult, if not impossible,&nbsp;to assess the
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| completeness of the set of Use Cases without the context provided by the associated Actors. Furthermore, missing an
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| actor may result in&nbsp;missing important stakeholder perspectives, resulting&nbsp;in a solution that does not meet
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| all&nbsp;stakeholder needs.
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| </p>
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| <p>
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| Hence, identifying the Actors for the system&nbsp;should be done early in the lifecycle.&nbsp;&nbsp;Actors are
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| captured, including their names, brief descriptions, and relationships to use cases,&nbsp;in the <a class="elementLinkWithType" href="./../../../openup/workproducts/uc_model_85965D1B.html" guid="_W2SgEDR5EdutE_HNDTJk5Q">Artifact: Use-Case Model</a>.
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| </p>
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| <h3>
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| Properties of Actors
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| </h3>
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| <h4>
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| Name
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| </h4>
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| <p>
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| Each actor should have a name that clearly describes the role played by the user.
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| </p>
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| <h4>
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| Brief Description
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| </h4>
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| <p>
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| Each actor should have a brief description that clearly describes:
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| </p>
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| <ul>
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| <li>
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| What or who the actor represents.
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| </li>
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| <li>
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| Why the actor is needed.
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| </li>
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| <li>
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| What interests the actor has in the system
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| </li>
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| <li>
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| Major characteristics of the actor.
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| </li>
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| </ul>
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| <p>
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| The major characteristics of the actor&nbsp;are important as they may influence how the system is developed, for
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| example characteristics of the user interface such as accessibility or globalization.&nbsp; Examples of important
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| characteristics include:
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| </p>
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| <ul>
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| <li>
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| The actors level of domain knowledge
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| </li>
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| <li>
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| The actors level of computer experience
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| </li>
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| <li>
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| The actors abilities and disabilities
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| </li>
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| <li>
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| The actors native language
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| </li>
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| </ul></mainDescription> |
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