Document Type Definition (DTD)

XML Language / Document Type Definition (DTD)

Document Type Definition (DTD)
It tells about the structure (root, containers, sub containers and elements) and their data types of an XML document. i.e DTD is used to verify that XML data is valid or not. It is used for exchanging data with a people who agrees on DTD standard.

DTD Data Types

Data Types	Details
CDATA	character data
ENTITY	Entity value
ENTITIES	Entities value
ID	unique id
IDREF	Id of another element
IDREFS	Id’s of another element
NMTOKEN	valid XML name value
NMTOKENS	valid XML names value
PCDATA	Parsed Character Data

DTD Data Types
1. Internal. 2. External.

Internal DTD Declaration
If the DTD is declared inside the XML file it is called internal DTD.

Internal DTD (save file with .xml extension. I.e IDTD.xml)

Explanation

Element	Define
!DOCTYPE languages	Root
!ELEMENT languages	languages
!ELEMENT textbookAuthornames	Container
!ELEMENT c	Sub Container
!ELEMENT Authorname	Element
!ELEMENT cpp	Sub Container

External DTD (save file with .xml extension. I.e EDTD.xml)
If the DTD is declared in an external file and reference to the DTD file is given xml then it is called as External DTD.

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