- 86 -
"undefined_notation">
Attribute Defaults
The last part of the attribute declaration list is the default value of the attribute. Defaults
come in four variations:
Required.
You must supply a value for the attribute (that is,
the document cannot leave
it blank).
Implied.
The parser tells the XML application that no value was supplied, and it is up to
the XML application
to decide what value, if any, to fill in.
Fixed.
The values of the attributes are included in the declaration itself. If no value is
supplied, the parser plugs in and passes on the default value.
If a value is supplied, it has
to be the same as specified in the declaration or else the parser issues an error.
Supplied.
In this case (the most common), the DTD supplies
the default value of the
attribute if it is not supplied in the XML document.
Let’s take a more detailed look at each default type.
