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| <org.eclipse.epf.uma:ContentDescription xmi:version="2.0" |
| xmlns:xmi="http://www.omg.org/XMI" xmlns:org.eclipse.epf.uma="http://www.eclipse.org/epf/uma/1.0.5/uma.ecore" |
| xmlns:epf="http://www.eclipse.org/epf" epf:version="1.5.0" xmlns:rmc="http://www.ibm.com/rmc" |
| rmc:version="7.5.0" xmi:id="-V_0kmI76XRz-UHHq2rP2Ag" |
| name="using_method_content_variability,_8YIMYCNQEdycLddDalDmbA" guid="-V_0kmI76XRz-UHHq2rP2Ag" |
| changeDate="2008-10-17T01:48:42.829-0700" version="7.1.0"> |
| <mainDescription><p>
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| This guideline explains how to utilize method content variability to modify an existing element without directly
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| changing the original element's base definition, or to create a new element based on an existing element. Changes are
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| defined in a separate content package or plug-in, and the original plug-in is kept intact. Thus, it allows you to
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| change method elements by simply changing a configuration (in other words, changing what plug-ins and packages are
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| included in the configuration).
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| </p>
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| <p>
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| Variability involves textual attributes and relationships.&nbsp; In other words you can use variability to add, delete
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| change, or reuse&nbsp;both text and relationships.&nbsp;
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| </p>
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| <p>
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| Variability is defined between two elements of the same type:
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| </p>
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| <ul>
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| <li>
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| Base element: The target of the variability; the element being changed (or used as a base for new element)
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| </li>
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| <li>
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| Variability element: The element containing the changes (or new content or relationships) to be combined with the
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| base
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| </li>
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| </ul>
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| <p>
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| The base element is never changed directly. All changes (or new content) is defined in the variability element. The
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| variability element specifies which element is the base.
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| </p>
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| <p>
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| As shown in Figure 1, when both the base element and the varaibility element are inlcluded in a configuration, the
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| configuration "resolves" the variability to produce the result, where that result depends on what variability was used.
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| </p>
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| <p>
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| <strong>Figure 1. Method content variability elements</strong><br />
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| </p><br />
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| <p>
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| <img alt="variability_elements" src="./resources/variability.gif" border="0" />&nbsp;
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| </p>
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| <p>
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| There are different types of variability, each with their own characteristics, rules, pros and cons. Table 1 provides a
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| summary of the different types of variability and when you might want to use them.<br />
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| <br />
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| </p>
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| <table title="Method Content Variability Summary" cellspacing="0" cellpadding="2" width="85%"
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| summary="summary of different types of method content variability" border="1">
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| <caption>
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| <strong>Table 1. Method Content Variability Summary</strong>
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| </caption>
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| <tbody>
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| <tr>
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| <td>
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| <strong>Variability Type</strong>
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| </td>
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| <td>
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| <strong>Result</strong>
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| </td>
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| <td>
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| <strong>Possible Uses</strong>
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| </td>
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| </tr>
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| <tr>
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| <td>
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| Contributes
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| </td>
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| <td>
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| <p>
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| Contributing element adds to the base element<br />
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| (result = base element plus contributed characteristics)
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| </p>
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| <ul>
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| <li>
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| Contributing (variability) element adds to the base element.
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| </li>
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| <li>
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| The base appears in the published Web site, but the contributing element does not.
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| </li>
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| <li>
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| Incoming and outgoing relationships from the contributing element are added to the base<br />
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| Exception: If the relationship is a "to one" relationship (for example, a task has at most one
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| primary performing role) then the relationship in the contributor is ignored if the base already
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| has one.
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| </li>
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| <li>
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| Text from the contributing element is appended to corresponding base sections.
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| </li>
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| <li>
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| A base element can have more then one contributor.
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| </li>
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| <li>
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| Contributes works transitively (a contributing element contributes its own contributors).
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| </li>
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| </ul>
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| </td>
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| <td>
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| <ul>
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| <li>
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| Add guidance to an existing element
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| </li>
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| <li>
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| Add steps to an existing task
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| </li>
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| <li>
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| Add responsibility for a work product to a role
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| </li>
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| <li>
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| Add a primary performing role to a task
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| </li>
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| <li>
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| Add a work product to a task (as an input or output work product)
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| </li>
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| <li>
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| Add text to existing elements
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| </li>
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| <li>
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| Adding method elements to existing categories<br />
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| <br />
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| </li>
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| </ul>
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| </td>
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| </tr>
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| <tr>
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| <td>
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| Replaces
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| </td>
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| <td>
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| <p>
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| Replacing element replaces parts of the base element (incoming relationships remain)<br />
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| (result = new element, no base element)
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| </p>
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| <ul>
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| <li>
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| Replacing (variability)&nbsp;element replaces parts of the base element.
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| </li>
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| <li>
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| The replacing element&nbsp;appears in the published Web site but the base element does not.
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| </li>
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| <li>
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| Outgoing relationships in the replacing element are maintained, and the base's are ignored.
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| </li>
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| <li>
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| Incoming relationships to the base are maintained and added to the replacing element.<br />
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| Exception: If the replacing element has an incoming to-one relationship (for example, a replacing a
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| role that includes a task performs the role relationship),&nbsp;the replacing element&nbsp;replaces
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| that relationship in the&nbsp;base element.
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| </li>
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| <li>
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| Text in the replacing element is left maintained, the base's text is ignored.
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| </li>
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| <li>
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| A base element can only be replaced by one replacing element at a time. If two elements replace the
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| same base element,&nbsp;only one can be used for interpretation (the plug-in containing one of the
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| replacing elements needs to be removed from the configuration or no replacement will take place).
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| </li>
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| <li>
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| Replacement works transitively (if a replacing element is replaced itself, then&nbsp;the final
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| replacing element will prevail).
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| </li>
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| </ul>
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| </td>
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| <td>
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| <ul>
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| <li>
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| Replace an existing method content element with another method content element
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| </li>
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| </ul>
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| </td>
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| </tr>
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| <tr>
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| <td>
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| Extends
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| </td>
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| <td>
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| <p>
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| Extending element inherits characteristics of the base element<br />
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| (result = base element + new element)
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| </p>
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| <ul>
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| <li>
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| Extending (variability) element inherits characteristics of the base element. The base element is
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| unchanged.
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| </li>
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| <li>
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| Both the extending element&nbsp;and the base appear in the published Web site.
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| </li>
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| <li>
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| Outgoing relationships from the base are added to the extending element.
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| </li>
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| <li>
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| Incoming relationships in the extending element&nbsp;are maintained, and the base's are ignored.
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| </li>
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| <li>
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| Text is included in the extending element from the base element if the extending element&nbsp;did
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| not include any text for the given section.
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| </li>
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| <li>
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| Extends works transitively (if an extending element is extended itself the second extension
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| inherits from its direct and indirect base elements).
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| </li>
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| </ul>
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| </td>
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| <td>
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| <ul>
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| <li>
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| Define a new element that looks just like an existing element, with some modifications (in other
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| words, define a variant or a specialization of an existing element)
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| </li>
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| <li>
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| Extends is not used to modify an existing element
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| </li>
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| </ul>
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| </td>
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| </tr>
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| <tr>
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| <td>
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| Extends-Replaces
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| </td>
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| <td>
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| <p>
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| Replacing element replaces only values that have been redefined in the replacer<br />
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| (result = new element, no base element)
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| </p>
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| <ul>
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| <li>
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| Combines the effects of extends and replaces variability, allowing you to selectively replace
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| specific attributes and relationships of the base element.
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| </li>
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| <li>
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| Extending-replacing (variability) element replaces values in the base element that have been
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| redefined in the&nbsp;extending-replacing element . All other values of the base element are
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| unaffected.
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| </li>
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| <li>
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| Both the extending-replacing element&nbsp;and the base appear in the published Web
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| site.&nbsp;&nbsp;
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| </li>
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| </ul>
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| </td>
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| <td>
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| <ul>
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| <li>
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| Rename an existing element
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| </li>
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| <li>
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| Replace a specific textual attribute of a method element
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| </li>
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| <li>
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| Replace the outgoing relationships of an existing method element
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| </li>
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| <li>
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| Replace the incoming relationships of an existing method element
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| </li>
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| </ul>
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| </td>
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| </tr>
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| </tbody>
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| </table>
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| <p>
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| For detailed information on how the different kinds of method content variability affect the different method element
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| relationships, see the attached spreadsheet (<a href="./resources/Variability%20Cheat%20Sheet.xls"
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| target="_blank">Variability Cheat Sheet.xls</a>).
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| </p>
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| <h3>
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| Order of Evaluation
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| </h3>
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| <p>
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| Contribution precedes replacement (the contributes relationship is resolved first, followed by the replaces
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| relationship). The evaluation of contribution and replacement is performed top-down in the specialization hierarchy.
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| </p>
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| <h3>
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| Handy Tricks
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| </h3>
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| <p>
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| If you ever find that you want to create an element that looks just like an existing element, but includes some
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| additional content, you can use a combination of extends and contributes to achieve the desired result.&nbsp; To do
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| this, perform the following steps:
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| </p>
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| <ol>
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| <li>
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| Define a method element that that extends the original base element. This results in a new element that looks just
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| like the original element.
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| </li>
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| <li>
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| Define another method element that contributes to the extending element and add the desired content. This results
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| in adding the new content to the new element that already includes the original content.
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| </li>
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| </ol>
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| <p>
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| The net resutl:&nbsp;A new element that includes the original content plus the new content.
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| </p></mainDescription> |
| </org.eclipse.epf.uma:ContentDescription> |
