1. Well-formed and Valid XML Documents
XML and Web Services (II/2546)
Well-formed and Valid XML Documents
Kanda Runapongsa
Dept. of Computer Engineering
Khon Kaen University
Dept. of Computer Engineering, Khon Kaen U.

2. 168493: XML and Web Services (II/2546)
Well-formed & Valid
Well-formed XML documents are the XML documents that obey XML syntax
Valid XML documents are the XML documents that follow the rules of the schema of XML documents
Well-formed XML documents do not need to be valid
168493: XML and Web Services (II/2546)

3. Well-formed XML Documents
XML and Web Services (II/2546)
Well-formed XML Documents
Must have XML Declaration
Must have the root element
Elements must have a closing tag
Elements must be properly nested
Element name of the end-tag must match with that of the start-tag
<b><i>text is bold and italic</b></i>
Not <b><i>text is bold and italic</b></i>
168493: XML and Web Services (II/2546)
Dept. of Computer Engineering, Khon Kaen U.

4. Well-formed XML Documents (Cont.)
Attribute values must always be quoted
Element and attribute names cannot be started with xml (for both uppercase and lowercase)
Special characters (< and &) cannot be used in text as they are used in markup
168493: XML and Web Services (II/2546)

5. Some Rules for Checking “Valid”
The value of attribute of ID type must be unique between all values of all ID attributes
The value of IDREF attribute must match the value of some ID attribute in the document
The value of IDREFS attribute can contain several references to elements with ID attribute separated with whitespaces.
168493: XML and Web Services (II/2546)

6. 168493: XML and Web Services (II/2546)
Examples
DTD:
<!ELEMENT AAA (#PCDATA)>
<!ATTLIST AAA id ID #REQUIRED>
<!ELEMENT BBB (#PCDATA)>
<!ATTLIST BBB ref IDREF #REQUIRED>
XML:
<AAA id=“1”>Hello</AAA>
<BBB ref=“1”>Hi</BBB>
168493: XML and Web Services (II/2546)