To enforce attribution properties of elements, you must add an attribute-list declaration to the DTD. The attribute-list declaration lists the names of all attributes; specifies the data type of all attributes; indicates whether the attribute is required or optional; and provides a default value if necessary. The syntax is as follows:

<!ATTLIST element attribute1 type1 default1
   attribute2 type2 default2
   attributet type 3 default3...>

OR

<!ATTLIST ELEMENT attribute1 type1 default1>
<!ATTLIST ELEMENT attribute2 type2 default2>
<!ATTLIST ELEMENT attribute3 type3 default3>

Attribute Types

Type	Syntax
String	attribute CDATA
Enumerated (list of possible values)	attribute (value1 | value2 | value3)
Tokenized (valid XML name)	attribute token ID - unique identifier for the attribute IDREF - references id of another element IDREFS - a list of id references separated by spaces NMTOKEN - name token whose value is restricted to a valid XML name ENTITY - a reference to an external file (i.e. non-XML data) ENTITIES - a list of entity references separated by spaces

Default Values

There are four possible defaults:

Attribute Default	Syntax
#REQUIRED	<!ATTLIST Customer CustID ID #REQUIRED>
#IMPLIED	<!ATTLIST Customer CustType (home | business) #IMPLIED>
"default"	Optional value. Syntax to have parser assume a value: <!ATTLIST Item ItemQty CDATA "1">
#FIXED "default"	Optional value. If an attribute value is specified, it must match the default value.

 

 

 

Edit Orders.xml and add the following code:

<!-- document type declaration follows -->

<!DOCTYPE Customers
[
   <!ELEMENT Customers (Customer+)>
   <!ELEMENT Customer (Name, Address, Phone, E-mail?, Orders)>
   <!ATTLIST Customer CustID ID #REQUIRED>
   <!ATTLIST Customer CustType (home | business) #IMPLIED>
   <!ELEMENT Name (#PCDATA)>
   <!ATTLIST Name Title (Mr. | Mrs. | Ms.) #IMPLIED>
   <!ELEMENT Address (#PCDATA)>
   <!ELEMENT Phone (#PCDATA)>
   <!ELEMENT E-mail (#PCDATA)>
   <!ELEMENT Orders (Order+)>
   <!ELEMENT Order (Order_date, Items)>
   <!ATTLIST Order OrderID ID #REQUIRED>
   <!ATTLIST Order OrderBy IDREF #REQUIRED>
   <!ELEMENT Items (Item+)>
   <!ELEMENT Order_date (#PCDATA)>
   <!ELEMENT Item (#PCDATA)>
   <!ATTLIST Item ItemPrice CDATA #REQUIRED>
   <!ATTLIST Item ItemQty CDATA "1">
]>

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