The following instructions were written for the Resource perspective, but they will also work in many other perspectives.
You can create an entity that reuses another entity. To do so, follow these steps:
You now have two entities with the exact same value.
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.
Now, if you need to change the copyright date, you only need to do so in one place, not two.
Note: Since you had to make the CopyrightDate entity a Parameter 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 XMLCopyrightDate with a value of %CopyrightDate; and use it instead in the XML file.
To use the entity in an XML document, you must use the ampersand & followed by the name of the entity, and then end with the semi-colon ;. So, in an XML document, if you were working with an even page, you would need to put this:
&XMLCopyrightDate;
to call the XMLCopyrightDate entity. Remember, you cannot call the CopyrightDate entity because you had to make it a Parameter entity in order to be able to reference it in the CompanyCopyright entity.
If you were working with an odd page, you would need to put this:
&CompanyCopyright;
to call the CompanyCopyright entity.