DTD (Document Type Definition)

Created: 2022-07-09
Tags: #fleeting

Abstract:

Defines

structure
legal elements
attributes
of XML document

Say, file named note.dtd

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

^- We use this DTD above to -^

validate info of some XML doc
making sure XML file conforms with rules of.dtd

Let's say we validate the XML doc note with note.dtd

<?xml version="1.0" encoding="UTF-8"?>  
<!DOCTYPE note SYSTEM "note.dtd">  
<note>  
    <to>falcon</to>  
    <from>feast</from>  
    <heading>hacking</heading>  
    <body>XXE attack</body>  
</note>

Process of how .DTD validates XML file

Basically explanation of the note.dtd file

!DOCTYPE note -> Defines root element of document named note

!ELEMENT note (to, from, heading, body)
^-> Defines that note element must contain:
to, from, heading, body

!ELEMENT to (#PCDATA) defines type element to be "#PCDATA"
!ELEMENT to (#)
Basically to, from, heading, body elements will be defined as "#PCDATA"

NOTE: #PCDATA means parseable character data.

DTD (Document Type Definition)

Abstract:

Process of how .DTD validates XML file

References