What is difference between XML Schema and DTD?

user_164299 0
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I have googled this question, but I do not understand clearly what is an XML schema and DTD (document type definition), and why the XML schema is more powerful compared to DTD.

Any guidance would be highly appreciated.

dtd schema xml
12 Answers

Similarities between XSD and DTD

both specify elements, attributes, nesting, ordering, #occurences

Differences between XSD and DTD

XSD also has data types, (typed) pointers, namespaces, keys and more.... unlike DTD

Moreover though XSD is little verbose its syntax is extension of XML, making it convenient to learn fast.

user_12695140

XML DTD

The purpose of a DTD is to define the structure of an XML document. It defines the structure with a list of legal elements:

<!ATTLIST contact type CDATA #IMPLIED>
<!ELEMENT address1 ( #PCDATA)>
<!ELEMENT city ( #PCDATA)>
<!ELEMENT state ( #PCDATA)>
<!ELEMENT zip ( #PCDATA)>

XML Schema

XML Schema enables schema authors to specify that element quantity’s data must be numeric or, even more specifically, an integer. In the following example I used string:

<xs:element name="note">
<xs:complexType>
  <xs:sequence>
    <xs:element name="address1" type="xs:string"/>
    <xs:element name="city" type="xs:string"/>
    <xs:element name="state" type="xs:string"/>
    <xs:element name="zip" type="xs:string"/>
  </xs:sequence>
</xs:complexType>

user_21964100

DTD can have only two types of data, the CDATA and the PCDATA. But in a schema you can use all the primitive data type that you use in the programming language and you have the flexibility of defining your own custom data types.

The developer building a schema can create custom data types based on the core data types and by using different operators and modifiers.

user_13298760
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