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| <title>Reusing the value of one entity in another entity</title> |
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| <h1 class="topictitle1">Reusing the value of one entity in another entity</h1> |
| <div><p>Reusing the value of an entity in another entity can save you time |
| in several ways. For example, if your value is long and complicated, it is |
| much faster to simply reuse an entity than manually type in your value each |
| time. As well, if the value changes, you only have to change it in one location.</p><div class="skipspace"><p>The following instructions were written for the |
| Resource perspective, but they will also work in many other perspectives. </p> |
| <p>You |
| can create an entity that reuses another entity. To do so, follow these steps:</p> |
| </div> |
| <ol><li class="skipspace"><span>Open your DTD in the DTD editor.</span></li> |
| <li class="skipspace"><span>Create an entity.</span> <ol type="a"><li><span>Type a name for the entity and select <span class="uicontrol">Parameter</span> from |
| the <span class="uicontrol">Entity type</span> list.</span></li> |
| <li><span>Type the value of the entity in the <span class="uicontrol">Entity Value</span> field.</span></li> |
| </ol> |
| </li> |
| <li class="skipspace"><span>Create another entity.</span><ol type="a"><li><span>Type a name and select <span class="uicontrol">General</span> from the <span class="uicontrol">Entity |
| type</span> list.</span></li> |
| <li><span>In the <span class="uicontrol">Entity Value</span> field, type a reference |
| to the first parameter entities' value (that is, type %<var class="varname">parmentityname</var>;)</span></li> |
| </ol> |
| </li> |
| </ol> |
| <div class="skipspace"><p>You now have two entities with the exact same value. </p> |
| </div> |
| <div class="skipspace">The following sample shows how you might create an entity that reuses |
| the value of another entity.<p>You need to place a copyright at the end of |
| every page of a book. On even pages, you need to put "Copyright 2003" and |
| on odd pages, you need to put "Copyright 2003. MyCompany Publishing." First |
| you will declare an entity with the simpler value and then create an entity |
| with the more complicated value.</p> |
| <ol><li>Open your DTD in the DTD editor.</li> |
| <li>Create an entity. In the <span class="uicontrol">Name</span> field, type <kbd class="userinput">CopyrightDate</kbd>. |
| Select <span class="uicontrol">Parameter</span> from the <span class="uicontrol">Entity type</span> list. |
| In the <span class="uicontrol">Entity Value</span>, type <kbd class="userinput">Copyright 2003</kbd>.</li> |
| <li>Create another entity. In the <span class="uicontrol">Name</span> field, type <kbd class="userinput">CompanyCopyright</kbd>. |
| Select <span class="uicontrol">General</span> from the <span class="uicontrol">Entity type</span> list. |
| In the<span class="uicontrol">Entity Value</span> field, type <kbd class="userinput">%CopyrightDate; |
| MyCompany Publishing</kbd>.</li> |
| </ol> |
| <p>Now, if you need to change the copyright date, you only need to do |
| so in one place, not two.</p> |
| <p> <b>Note</b>: Since you had to make the CopyrightDate |
| entity a <span class="uicontrol">Parameter</span> entity in order to be able to reference |
| it in the CompanyCopyright entity, you cannot use it in an XML file. |
| You would have to create a third entity called <kbd class="userinput">XMLCopyrightDate</kbd> with |
| a value of <kbd class="userinput">%CopyrightDate;</kbd> and use it instead in the |
| XML file.</p> |
| <p>To use the entity in an XML document, you must use the ampersand <kbd class="userinput">&</kbd> followed |
| by the name of the entity, and then end with the semi-colon <kbd class="userinput">;</kbd>. |
| So, in an XML document, if you were working with an even page, you would need |
| to put this:</p> |
| <p><kbd class="userinput">&XMLCopyrightDate; </kbd></p> |
| <p> to |
| call the XMLCopyrightDate entity. Remember, you cannot call the CopyrightDate |
| entity because you had to make it a <span class="uicontrol">Parameter</span> entity |
| in order to be able to reference it in the CompanyCopyright entity.</p> |
| <p>If |
| you were working with an odd page, you would need to put this:</p> |
| <p><kbd class="userinput">&CompanyCopyright; </kbd></p> |
| <p> to |
| call the CompanyCopyright entity.</p> |
| </div> |
| </div> |
| |
| <div> |
| <p> |
| <b class="parentlink">Parent topic:</b> <a href="../topics/tcretent.html" title="An entity is a shortcut used to represent complex strings or symbols that would otherwise be impossible, difficult or repetitive to include by hand.">Creating entities</a><br /> |
| </p> |
| <p><b class="reltaskshd">Related tasks</b><br /> |
| <a href="../topics/trusintp.html" title="Reusing parameter entities in attributes can save you a lot of time. If you have several elements using the exact same attribute, you only have to input the information once (into an entity). ">Reusing internal parameter entities in an attribute name or type</a><br /> |
| <a href="../topics/trusextp.html" title="Using an entity in a content model can save you time if you want to have the same information in several content models. You can create a DTD that references another DTD and then declares an element whose content model refers to a parameter entity created in another DTD.">Reusing external parameter entities in an element's content model</a><br /> |
| </p> |
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