| Attribute List Declaration |
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<!ATTLIST element_name [attribute_name attribute_type default_decl]*>
In a valid XML document, it is
necessary to declare the attribute names, types, and default values
that are used with each element type.
The attribute name must obey the rules for XML names, and no
duplicate attribute names may exist within a single declaration.
Attributes
are declared as having a specific type. Depending on the declared
type, a validating XML parser will constrain the values that appear
in instances of those attributes within a document. The following
table lists the various attribute types and their meanings:
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Attribute type
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Meaning
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CDATA
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Simple character data.
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ID
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A unique ID value within the current XML document.
No two ID attribute values within a document can
have the same value, and no element can have two attributes of type
ID.
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IDREF,
IDREFS
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A single reference to an element ID
(IDREF) or a list of IDs
(IDREFS), separated by spaces. Every
ID token must refer to a valid
ID located somewhere within the document that
appears as the ID type
attribute's value.
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ENTITY,
ENTITIES
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A single reference to a declared unparsed external entity
(ENTITY) or a list of references
(ENTITIES), separated by whitespace.
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NMTOKEN, NMTOKENS
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A single name token value (NMTOKEN) or a list of
name tokens (NMTOKENS), separated by spaces.
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