Description of Attribute Properties in DTDs

Table 90 shows the properties that an attribute can have. It also provides the possible values, and a description for each property.

Table 90. Attribute Property Descriptions
Property
Allowable Values
Description
Type
Attribute
All attribute nodes have this type.
Name
String
Identifier for the particular attribute.
Restrictions
Fixed
The attribute is required and it must always have the value specified by the Default property. You must always explicitly specify this attribute.
 
Implied
The attribute is optional. There is no default value.
 
Optional
The attribute is optional. If you do not specify it, the XML parser uses the value of the Default property.
 
Required
The element must always explicitly specify this attribute and assign a value to it.
Content Type
CDATA
The attribute value can contain any valid character data. It is a text string.
 
Entity
The attribute value is the name of an entity defined in the DTD.
 
Entities
The attribute value is a space-separated list of entities that are defined in the DTD.
 
Enumerated
The attribute value is one of a set of specified values. When the value of the Content Type property is Enumerated, the attribute has an additional property: Allowed Values. Specify the allowed values in a space-separated list.
 
ID
The attribute value is a unique name within the DTD.
 
IDREF
The attribute value is an ID that is defined in the DTD.
 
IDREFs
The attribute value is a space-separated list of IDs that are defined in the DTD.
 
NMToken
The attribute value is a valid XML name that is composed of letters, numbers, hyphens, underscores, and colons.
 
NMTokens
The attribute value is a space-separated list of name tokens.
 
Notation
The name of a notation specified in the DTD. The notation describes a non-XML data format, such as those used for image files. When the value of the Content Type property is Notation, the attribute has an additional property: Allowed Values. Specify the allowed values in a space-separated list.
 
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