HTML Quick Reference - HTML5 and CSS Comprehensive - page 700

Table H-19 DTD Data Type Attributes

Modifier Description

#DEFAULT value Specific value set at the default attribute value

#FIXED "value" Attribute value is fixed and must always take the default value assigned

#IMPLIED Attribute value is optional; if used in an element type, no default value is supplied

#REQUIRED Attribute value must be specified with the element

Entity Declarations
As just discussed, a DTD can also include entity declarations , which assign a name
to a block of text or other characters that can be interpreted as markup language and
substituted in a document. The replacement text must begin with an ampersand (&) and
end with a semicolon (;). Entity declarations can be internal or external. Table H-20 shows
the general form of an internal entity declaration. Table H-21 shows the predefined symbols
that can be used in an entity declaration.

Table H-20 General Form of Internal Entity Declaration

General form: <!ENTITY name "&replacement;">

<ELEMENT>text "&replacement;"</ELEMENT>

Comment: The attribute name is a valid element name and replacement is the entity characters to be

substituted within the string. Circular references are not allowed.

Example: <!ENTITY copyright "&#xA9;">

<PUBLISHED>2014 Cengage Learning &copyright;</PUBLISHED>

Table H-21 Predefined Entity Symbols

Entity Symbol Explanation

&amp; & Cannot be used in processing instructions

&lt; < Use with attributes beginning with quotation marks

&gt; > Use after ]] in normal text and processing instructions

&quot; “ Use in attributes within double quotation marks

&apos; ' Use in attributes within single quotation marks

&#x hex ; [varied] Where hex is replaced with a hexadecimal value for a character, such as

A9 for the copyright symbol (©)

XML allows the use of external entities to refer to the contents of another file.
An external entity exists at a specified location or URL. The content of the external
file is inserted at the point of reference and parsed as part of the referring document.
Table H-22 shows the general form of an external entity.

Table H-22 General Form of an External Entity

General form: <!ENTITY name PUBLIC/SYSTEM "URI/URL">

<ELEMENT>text "&replacement;" </ELEMENT>

Comment: The attribute name is a valid element name; the URI or URL is an identifier that points to a file

on that system or a public file available via URL. ENTITY must be declared first.

Example: <!ENTITY stockquotes SYSTEM

"www.cnbc.com/id/26272770/site/14081545/">
<inances>
<dowjones>Dow Jones Industrial Averages</dowjones>
&stockquotes;
</inances>