XML in a Nutshell, 3rd Edition

General Entity Declarations

As you learned in Chapter 2, XML predefines five entities for your convenience:

<

The less-than sign, a.k.a. the opening angle bracket (<)

&

The ampersand (&)

>

The greater-than sign, a.k.a. the closing angle bracket (>)

"

The straight, double quotation marks (“)

'

The apostrophe, a.k.a. the straight single quote (')

The DTD can define many more entities. This is useful not just in valid documents, but even in documents you don’t plan to validate.

Entity references are defined with an ENTITY declaration in the DTD. This gives the name of the entity, which must be an XML name, and the replacement text of the entity. For example, this entity declaration defines &super; as an abbreviation for supercalifragilisticexpialidocious:

<!ENTITY super "supercalifragilisticexpialidocious">

Once that’s done, you can use &super; anywhere you’d normally have to type the entire word (and probably misspell it).

Entities can contain markup as well as text. For example, this declaration defines &footer; as an abbreviation for a standard web page footer that will be repeated on many pages:

<!ENTITY footer '<hr size="1" noshade="true"/> <font CLASS="footer"> <a href="index.html">O&apos;Reilly Home</a> | <a href="sales/bookstores/">O&apos;Reilly Bookstores</a> | <a href="order_new/">How to Order</a> | <a href="oreilly/contact.html">O&apos;Reilly Contacts</a><br> <a href="http://international.oreilly.com/">International</a> | <a href="oreilly/about.html">About O&apos;Reilly</a> ...