The DOCTYPE Declaration

A document type declaration contains internal markup declarations or points to external markup declarations that provide a grammar for validating a given document or class of documents.

Productions

[28] doctypedecl ::= '<!DOCTYPE' S Name (S ExternalID)? S? ('[' intSubset ']' S?)? '>'
[28a] DeclSep ::= PEReference | S
[28b] intSubset ::= (markupdecl | DeclSep)*
[29] markupdecl ::= elementdecl | AttlistDecl | EntityDecl | NotationDecl | PI |
Comment

Examples

<!DOCTYPE message SYSTEM "myMessage.dtd" >

<!DOCTYPE message SYSTEM "http://www.example.com/DTD/myMessage.dtd" >

<!DOCTYPE html PUBLIC "-//W3C/DTD XHTML 1.0 Strict//EN" "http://www.w3.org/
TR/xhtml1/DTD/xhtml1-strict.dtd" >

<!DOCTYPE message [
  <!ELEMENT message (#PCDATA) >
  <!ATTLIST message date CDATA #REQUIRED >
]>

<!DOCTYPE message SYSTEM "myMessage.dtd" [
  <!ATTLIST message info CDATA #IMPLIED >
]>

Description

A document type or DOCTYPE declaration provides information to a validating XML parser about how to validate an XML document. The DOCTYPE keyword appears first; then the document, or root, element of the document being validated is identified, followed by either a SYSTEM or PUBLIC identifier.

SYSTEM indicates that the DTD will be found as indicated in the filename or URI that follows (also called a system literal; for example, "myMessage.dtd" or "http://www.example.com/DTD/myMessage.dtd“).

PUBLIC hints that the DTD is standard, well known, and widely available—although technically, it just means that a ...

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