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    rmc:version="7.5.0" xmi:id="-V_0kmI76XRz-UHHq2rP2Ag"
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    changeDate="2008-10-17T01:48:42.829-0700" version="7.1.0">
  <mainDescription>&lt;p>&#xD;
    This guideline explains how to utilize method content variability to modify an existing element without directly&#xD;
    changing the original element's base definition, or to create a new element based on an existing element. Changes are&#xD;
    defined in a separate content package or plug-in, and the original plug-in is kept intact. Thus, it allows you to&#xD;
    change method elements by simply changing a configuration (in other words, changing what plug-ins and packages are&#xD;
    included in the configuration).&#xD;
&lt;/p>&#xD;
&lt;p>&#xD;
    Variability involves textual attributes and relationships.&amp;nbsp; In other words you can use variability to add, delete&#xD;
    change, or reuse&amp;nbsp;both text and relationships.&amp;nbsp;&#xD;
&lt;/p>&#xD;
&lt;p>&#xD;
    Variability is defined between two elements of the same type:&#xD;
&lt;/p>&#xD;
&lt;ul>&#xD;
    &lt;li>&#xD;
        Base element: The target of the variability; the element being changed (or used as a base for new element)&#xD;
    &lt;/li>&#xD;
    &lt;li>&#xD;
        Variability element: The element containing the changes (or new content or relationships) to be combined with the&#xD;
        base&#xD;
    &lt;/li>&#xD;
&lt;/ul>&#xD;
&lt;p>&#xD;
    The base element is never changed directly. All changes (or new content) is defined in the variability element. The&#xD;
    variability element specifies which element is the base.&#xD;
&lt;/p>&#xD;
&lt;p>&#xD;
    As shown in Figure 1, when both the base element and the varaibility element are inlcluded in a configuration, the&#xD;
    configuration &quot;resolves&quot; the variability to produce the result, where that result depends on what variability was used.&#xD;
&lt;/p>&#xD;
&lt;p>&#xD;
    &lt;strong>Figure 1. Method content variability elements&lt;/strong>&lt;br />&#xD;
&lt;/p>&lt;br />&#xD;
&lt;p>&#xD;
    &lt;img alt=&quot;variability_elements&quot; src=&quot;./resources/variability.gif&quot; border=&quot;0&quot; />&amp;nbsp;&#xD;
&lt;/p>&#xD;
&lt;p>&#xD;
    There are different types of variability, each with their own characteristics, rules, pros and cons. Table 1 provides a&#xD;
    summary of the different types of variability and when you might want to use them.&lt;br />&#xD;
    &lt;br />&#xD;
&lt;/p>&#xD;
&lt;table title=&quot;Method Content Variability Summary&quot; cellspacing=&quot;0&quot; cellpadding=&quot;2&quot; width=&quot;85%&quot;&#xD;
summary=&quot;summary of different types of method content variability&quot; border=&quot;1&quot;>&#xD;
    &lt;caption>&#xD;
        &lt;strong>Table 1. Method Content Variability Summary&lt;/strong>&#xD;
    &lt;/caption>&#xD;
    &lt;tbody>&#xD;
        &lt;tr>&#xD;
            &lt;td>&#xD;
                &lt;strong>Variability Type&lt;/strong>&#xD;
            &lt;/td>&#xD;
            &lt;td>&#xD;
                &lt;strong>Result&lt;/strong>&#xD;
            &lt;/td>&#xD;
            &lt;td>&#xD;
                &lt;strong>Possible Uses&lt;/strong>&#xD;
            &lt;/td>&#xD;
        &lt;/tr>&#xD;
        &lt;tr>&#xD;
            &lt;td>&#xD;
                Contributes&#xD;
            &lt;/td>&#xD;
            &lt;td>&#xD;
                &lt;p>&#xD;
                    Contributing element adds to the base element&lt;br />&#xD;
                    (result = base element plus contributed characteristics)&#xD;
                &lt;/p>&#xD;
                &lt;ul>&#xD;
                    &lt;li>&#xD;
                        Contributing (variability) element adds to the base element.&#xD;
                    &lt;/li>&#xD;
                    &lt;li>&#xD;
                        The base appears in the published Web site, but the contributing element does not.&#xD;
                    &lt;/li>&#xD;
                    &lt;li>&#xD;
                        Incoming and outgoing relationships from the contributing element are added to the base&lt;br />&#xD;
                        Exception: If the relationship is a &quot;to one&quot; relationship (for example, a task has at most one&#xD;
                        primary performing role) then the relationship in the contributor is ignored if the base already&#xD;
                        has one.&#xD;
                    &lt;/li>&#xD;
                    &lt;li>&#xD;
                        Text from the contributing element is appended to corresponding base sections.&#xD;
                    &lt;/li>&#xD;
                    &lt;li>&#xD;
                        A base element can have more then one contributor.&#xD;
                    &lt;/li>&#xD;
                    &lt;li>&#xD;
                        Contributes works transitively (a contributing element contributes its own contributors).&#xD;
                    &lt;/li>&#xD;
                &lt;/ul>&#xD;
            &lt;/td>&#xD;
            &lt;td>&#xD;
                &lt;ul>&#xD;
                    &lt;li>&#xD;
                        Add guidance to an existing element&#xD;
                    &lt;/li>&#xD;
                    &lt;li>&#xD;
                        Add steps to an existing task&#xD;
                    &lt;/li>&#xD;
                    &lt;li>&#xD;
                        Add responsibility for a work product to a role&#xD;
                    &lt;/li>&#xD;
                    &lt;li>&#xD;
                        Add a primary performing role to a task&#xD;
                    &lt;/li>&#xD;
                    &lt;li>&#xD;
                        Add a work product to a task (as an input or output work product)&#xD;
                    &lt;/li>&#xD;
                    &lt;li>&#xD;
                        Add text to existing elements&#xD;
                    &lt;/li>&#xD;
                    &lt;li>&#xD;
                        Adding method elements to existing categories&lt;br />&#xD;
                        &lt;br />&#xD;
                    &lt;/li>&#xD;
                &lt;/ul>&#xD;
            &lt;/td>&#xD;
        &lt;/tr>&#xD;
        &lt;tr>&#xD;
            &lt;td>&#xD;
                Replaces&#xD;
            &lt;/td>&#xD;
            &lt;td>&#xD;
                &lt;p>&#xD;
                    Replacing element replaces parts of the base element (incoming relationships remain)&lt;br />&#xD;
                    (result = new element, no base element)&#xD;
                &lt;/p>&#xD;
                &lt;ul>&#xD;
                    &lt;li>&#xD;
                        Replacing (variability)&amp;nbsp;element replaces parts of the base element.&#xD;
                    &lt;/li>&#xD;
                    &lt;li>&#xD;
                        The replacing element&amp;nbsp;appears in the published Web site but the base element does not.&#xD;
                    &lt;/li>&#xD;
                    &lt;li>&#xD;
                        Outgoing relationships in the replacing element are maintained, and the base's are ignored.&#xD;
                    &lt;/li>&#xD;
                    &lt;li>&#xD;
                        Incoming relationships to the base are maintained and added to the replacing element.&lt;br />&#xD;
                        Exception: If the replacing element has an incoming to-one relationship (for example, a replacing a&#xD;
                        role that includes a task performs the role relationship),&amp;nbsp;the replacing element&amp;nbsp;replaces&#xD;
                        that relationship in the&amp;nbsp;base element.&#xD;
                    &lt;/li>&#xD;
                    &lt;li>&#xD;
                        Text in the replacing element is left maintained, the base's text is ignored.&#xD;
                    &lt;/li>&#xD;
                    &lt;li>&#xD;
                        A base element can only be replaced by one replacing element at a time. If two elements replace the&#xD;
                        same base element,&amp;nbsp;only one can be used for interpretation (the plug-in containing one of the&#xD;
                        replacing elements needs to be removed from the configuration or no replacement will take place).&#xD;
                    &lt;/li>&#xD;
                    &lt;li>&#xD;
                        Replacement works transitively (if a replacing element is replaced itself, then&amp;nbsp;the final&#xD;
                        replacing element will prevail).&#xD;
                    &lt;/li>&#xD;
                &lt;/ul>&#xD;
            &lt;/td>&#xD;
            &lt;td>&#xD;
                &lt;ul>&#xD;
                    &lt;li>&#xD;
                        Replace an existing method content element with another method content element&#xD;
                    &lt;/li>&#xD;
                &lt;/ul>&#xD;
            &lt;/td>&#xD;
        &lt;/tr>&#xD;
        &lt;tr>&#xD;
            &lt;td>&#xD;
                Extends&#xD;
            &lt;/td>&#xD;
            &lt;td>&#xD;
                &lt;p>&#xD;
                    Extending element inherits characteristics of the base element&lt;br />&#xD;
                    (result = base element + new element)&#xD;
                &lt;/p>&#xD;
                &lt;ul>&#xD;
                    &lt;li>&#xD;
                        Extending (variability) element inherits characteristics of the base element. The base element is&#xD;
                        unchanged.&#xD;
                    &lt;/li>&#xD;
                    &lt;li>&#xD;
                        Both the extending element&amp;nbsp;and the base appear in the published Web site.&#xD;
                    &lt;/li>&#xD;
                    &lt;li>&#xD;
                        Outgoing relationships from the base are added to the extending element.&#xD;
                    &lt;/li>&#xD;
                    &lt;li>&#xD;
                        Incoming relationships in the extending element&amp;nbsp;are maintained, and the base's are ignored.&#xD;
                    &lt;/li>&#xD;
                    &lt;li>&#xD;
                        Text is included in the extending element from the base element if the extending element&amp;nbsp;did&#xD;
                        not include any text for the given section.&#xD;
                    &lt;/li>&#xD;
                    &lt;li>&#xD;
                        Extends works transitively (if an extending element is extended itself the second extension&#xD;
                        inherits from its direct and indirect base elements).&#xD;
                    &lt;/li>&#xD;
                &lt;/ul>&#xD;
            &lt;/td>&#xD;
            &lt;td>&#xD;
                &lt;ul>&#xD;
                    &lt;li>&#xD;
                        Define a new element that looks just like an existing element, with some modifications (in other&#xD;
                        words, define a variant or a specialization of an existing element)&#xD;
                    &lt;/li>&#xD;
                    &lt;li>&#xD;
                        Extends is not used to modify an existing element&#xD;
                    &lt;/li>&#xD;
                &lt;/ul>&#xD;
            &lt;/td>&#xD;
        &lt;/tr>&#xD;
        &lt;tr>&#xD;
            &lt;td>&#xD;
                Extends-Replaces&#xD;
            &lt;/td>&#xD;
            &lt;td>&#xD;
                &lt;p>&#xD;
                    Replacing element replaces only values that have been redefined in the replacer&lt;br />&#xD;
                    (result = new element, no base element)&#xD;
                &lt;/p>&#xD;
                &lt;ul>&#xD;
                    &lt;li>&#xD;
                        Combines the effects of extends and replaces variability, allowing you to selectively replace&#xD;
                        specific attributes and relationships of the base element.&#xD;
                    &lt;/li>&#xD;
                    &lt;li>&#xD;
                        Extending-replacing (variability) element replaces values in the base element that have been&#xD;
                        redefined in the&amp;nbsp;extending-replacing element . All other values of the base element are&#xD;
                        unaffected.&#xD;
                    &lt;/li>&#xD;
                    &lt;li>&#xD;
                        Both the extending-replacing element&amp;nbsp;and the base appear in the published Web&#xD;
                        site.&amp;nbsp;&amp;nbsp;&#xD;
                    &lt;/li>&#xD;
                &lt;/ul>&#xD;
            &lt;/td>&#xD;
            &lt;td>&#xD;
                &lt;ul>&#xD;
                    &lt;li>&#xD;
                        Rename an existing element&#xD;
                    &lt;/li>&#xD;
                    &lt;li>&#xD;
                        Replace a specific textual attribute of a method element&#xD;
                    &lt;/li>&#xD;
                    &lt;li>&#xD;
                        Replace the outgoing relationships of an existing method element&#xD;
                    &lt;/li>&#xD;
                    &lt;li>&#xD;
                        Replace the incoming relationships of an existing method element&#xD;
                    &lt;/li>&#xD;
                &lt;/ul>&#xD;
            &lt;/td>&#xD;
        &lt;/tr>&#xD;
    &lt;/tbody>&#xD;
&lt;/table>&#xD;
&lt;p>&#xD;
    For detailed information on how the different kinds of method content variability affect the different method element&#xD;
    relationships, see the attached spreadsheet (&lt;a href=&quot;./resources/Variability%20Cheat%20Sheet.xls&quot;&#xD;
    target=&quot;_blank&quot;>Variability Cheat Sheet.xls&lt;/a>).&#xD;
&lt;/p>&#xD;
&lt;h3>&#xD;
    Order of Evaluation&#xD;
&lt;/h3>&#xD;
&lt;p>&#xD;
    Contribution precedes replacement (the contributes relationship is resolved first, followed by the replaces&#xD;
    relationship). The evaluation of contribution and replacement is performed top-down in the specialization hierarchy.&#xD;
&lt;/p>&#xD;
&lt;h3>&#xD;
    Handy Tricks&#xD;
&lt;/h3>&#xD;
&lt;p>&#xD;
    If you ever find that you want to create an element that looks just like an existing element, but includes some&#xD;
    additional content, you can use a combination of extends and contributes to achieve the desired result.&amp;nbsp; To do&#xD;
    this, perform the following steps:&#xD;
&lt;/p>&#xD;
&lt;ol>&#xD;
    &lt;li>&#xD;
        Define a method element that that extends the original base element. This results in a new element that looks just&#xD;
        like the original element.&#xD;
    &lt;/li>&#xD;
    &lt;li>&#xD;
        Define another method element that contributes to the extending element and add the desired content. This results&#xD;
        in adding the new content to the new element that already includes the original content.&#xD;
    &lt;/li>&#xD;
&lt;/ol>&#xD;
&lt;p>&#xD;
    The net resutl:&amp;nbsp;A new element that includes the original content plus the new content.&#xD;
&lt;/p></mainDescription>
</org.eclipse.epf.uma:ContentDescription>