Web Design in a Nutshell, 3rd Edition

Entity declarations

In XML, an entity is a string of characters that stands for something else. An entity can be used to represent a single character or a selection of marked up content, such as a footer containing copyright information. Entity declarations provide the name of the entity (which must be a legal XML name; see the earlier sidebar "XML Names“) and its replacement text. The five character entities proved by XML were listed in Table 7-1.

General entities insert replacement text into the body of an XML document. The syntax for declaring general entities is:

<!ENTITY address "1005 Gravenstein Highway, North Sebastopol, CA 95472">

As a result, wherever the author places an &address; entity in the XML source, it will be replaced by the full address upon display. The content may include markup tags. (Be sure that when double quotes are used to delimit the entity value, single quotes are used in the enclosed content, or vice versa.) The content of an entity may also reside in a separate, external file that is referenced in the entity declaration by its URL.

The XHTML sample at the beginning of this section includes another kind of entity called a parameter entity, shown here:

<!ENTITY % i18n
 "lang        %LanguageCode; #IMPLIED
  xml:lang    %LanguageCode; #IMPLIED
  dir         (ltr|rtl)      #IMPLIED"
  >

Parameter entities are used only within the DTD itself to declare groups of elements or entities that are repeated throughout the DTD. They are indicated by the % symbol (rather than &). The entity declaration ...