Defining Valid Element Attributes
May 3, 1999
Well, as you might expect, just as you use the DTD to define
valid elements, you also use the DTD to define valid element
attributes.
We already went over attributes in the last section, but to
refresh your memory, we used the following example where
STYLE and COLORING were attributes of the SHOE element.
<SHOE STYLE = "SPECTATOR" COLORING = "BLACK_AND_WHITE">
To declare attributes in the DTD you use the general format of:
<!ATTLIST ELEMENT_NAME ATTRIBUTE_NAME TYPE DEFAULT_VALUE>
ELEMENT_NAME is equal to the element in which the attribute
appears such as "SHOE" in the example above.
ATTRIBUTE_NAME is equal to the name of the attribute such as
"STYLE" or "COLORING" in the example above.
DEFAULT_VALUE specifies the value that is used if none is
specified by the document author.
TYPE specifies one of ten valid attribute types.
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NOTE: Since ATTLIST is a list it can have repeated attribute parts
(and often does). Consider the following ATTLIST definition.
<!ATTLIST Port
name NMTOKEN #REQUIRED
hostName NMTOKEN #IMPLIED
function %funcType; #REQUIRED
number CDATA #REQUIRED
type %serverType;
serverPort %fbool;
%basicAttrs;>
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Of the four pieces, TYPE and DEFAULT_VALUE require some
discusison. Let's look at DEFAULT VALUES first.
Empty Elements
Introduction to XML For Web Developers | Table of Contents
Attribute Defaults
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