김태정, All on Voiceportal : XML Validation

"Well Formed" XML과 DTD에 대한 이야기다.

XML with correct syntax is "Well Formed" XML.
XML validated against a DTD is "Valid" XML.

Well Formed XML documents

"Well Formed" XML document는 correct XML syntax를 가진다.

Syntax rules
- XML document는 root element를 가진다.
- XML elements는 closing tag가 있어야 한다.
- XML tags는 case sensitive 하다.
- XML elements는 properly nested이어야 한다.
- XML attribute values는 quoted 되어야 한다.

<?xml version="1.0" encoding="ISO-8859-1"?>
<note>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note>

Valid XML Documents

"Valid" XML document는 Document Type Definition(DTD)의 rules을 따르는 "Well Formed" XML documents를 말한다.

<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE note SYSTEM "Note.dtd">
<note>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note>

XML DTD

DTD의 목적은 XML문서의 구조를 정의하기 위한 것이다.

<!DOCTYPE note [
<!ELEMENT note (to,from,heading,body)>
<!ELEMENT to    (#PCDATA)>
<!ELEMENT from    (#PCDATA)>
<!ELEMENT heading (#PCDATA)>
<!ELEMENT body    (#PCDATA)>
]>

XML Schema

W3C supports an XML based alternative to DTD called XML Schema

<xs:element name="note"><xs:complexType>
<xs:sequence>
<xs:element name="to"    type="xs:string"/>
<xs:element name="from"    type="xs:string"/>
<xs:element name="heading" type="xs:string"/>
<xs:element name="body"    type="xs:string"/>
</xs:sequence>
</xs:complexType>
</xs:element>