XML guide-XML Validation

Source: Internet
Author: User


Syntax-compliant XML documents are well-structured XML documents.
An XML document verified by DTD is a valid XML document.

"Well-structured" XML document
A well-structured XML document should use the correct syntax.
A well-structured XML document should comply with XML syntax rules. The example given in the previous chapter is a well-structured XML document:
<? XML version = "1.0" encoding = "ISO-8859-1"?>
<Note>
<To> Tove </to>
<From> Jani </from>
<Heading> reminder <Body> don't forget me this weekend! </Body>
</Note>

"Valid" XML document
A valid XML document must comply with the DTD description.
A valid XML document is also a well-structured XML document and must comply with the DTD rules.
<? XML version = "1.0" encoding = "ISO-8859-1"?>
<! Doctype note system "internalnote. DTD">
<Note>
<To> Tove </to>
<From> Jani </from>
<Heading> reminder <Body> don't forget me this weekend! </Body>
</Note>

XML DTD
DTD defines valid elements available in XML documents.
The intention of DTD is to define the legal building module of the XML document. He defines a series of legal elements to determine the internal structure of the XML document. A well-structured XML document is not necessarily a valid XML document, but a valid XML document must be a well-structured XML document. For more information about DTD, see the DTD guide.

XML Schema
XML schema is a substitute for XML-based DTD.
W3C allows DTD and schema to replace each other. Readers can learn more in the schema guide.

Error
Errors in XML documents will cause XMLProgramStop.
W3C XML specification Declaration: if a program finds a valid error in processing XML documents, the program should be terminated. This is why the XML software is easier to write. All XML documents should be consistent.
In HTML, HTML files may contain many errors (for example, an element has a start tag without an end tag), which is also a reason for the huge size of HTML browsers, when they find an error, they have different methods to determine how the HTML file should be displayed.
This will never happen in XML.

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