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