Difference between PCDATA and CDATA in DTD

Question

What is the difference between  PCDATA and  CDATA in DTD

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PCDATA - Parsed Character Data

XML parsers normally parse all the text in an XML document.

CDATA - (Unparsed) Character Data

The term CDATA is used about text data that should not be parsed by the XML parser.

Characters like "<" and "&" are illegal in XML elements.

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PCDATA is text that will be parsed by a parser  Tags inside the text will be treated as markup and entities will be expanded   CDATA is text that will not be parsed by a parser  Tags inside the text will not be treated as markup and entities will not be expanded    By default  everything is PCDATA  In the following example  ignoring the root   lt bar gt  will be parsed  and it ll have no content  but one child     lt  xml version  1 0   gt   lt foo gt   lt bar gt  lt test gt content  lt  test gt  lt  bar gt   lt  foo gt    When we want to specify that an element will only contain text  and no child elements  we use the keyword PCDATA  because this keyword specifies that the element must contain parsable character data     that is   any text except the characters less-than   lt     greater-than   gt     ampersand   amp    quote    and double quote       In the next example   lt bar gt  contains CDATA  Its content will not be parsed and is thus  lt test gt content  lt  test gt     lt  xml version  1 0   gt   lt foo gt   lt bar gt  lt   CDATA  lt test gt content  lt  test gt    gt  lt  bar gt   lt  foo gt    There are several content models in SGML  The  PCDATA content model says that an element may contain plain text  The  parsed  part of it means that markup  including PIs  comments and SGML directives  in it is parsed instead of displayed as raw text  It also means that entity references are replaced   Another type of content model allowing plain text contents is CDATA  In XML  the element content model may not implicitly be set to CDATA  but in SGML  it means that markup and entity references are ignored in the contents of the element  In attributes of CDATA type however  entity references are replaced   In XML   PCDATA is the only plain text content model  You use it if you at all want to allow text contents in the element  The CDATA content model may be used explicitly through the CDATA block markup in  PCDATA  but element contents may not be defined as CDATA per default   In a DTD  the type of an attribute that contains text must be CDATA  The CDATA keyword in an attribute declaration has a different meaning than the CDATA section in an XML document  In a CDATA section all characters are legal  including  lt   gt   amp    and   characters   except the    gt  end tag    PCDATA is not appropriate for the type of an attribute  It is used for the type of  leaf  text    PCDATA is prepended by a hash in the content model to distinguish this keyword from an element named PCDATA  which would be perfectly legal

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From here  Google is your friend       In a DTD  PCDATA and CDATA are used to   assert something about the allowable   content of elements and attributes    respectively  In an element s content   model   PCDATA says that the element   contains  may contain   any old text      With exceptions as noted below   In   an attribute s declaration  CDATA is   one sort of constraint you can put on   the attribute s allowable values    other sorts  all mutually exclusive    include ID  IDREF  and NMTOKEN   An   attribute whose allowable values are   CDATA can  like PCDATA in an element    contain  any old text        A potentially really confusing issue   is that there s another  CDATA     also referred to as marked sections  A   marked section is a portion of element     PCDATA  content delimited with   special strings   to close it  If you   remember that PCDATA is  parsed   character data   a CDATA section is   literally the same thing  without the    parsed   Parsers transmit the content   of a marked section to downstream   applications without hiccupping every   time they encounter special characters   like  lt  and  amp   This is useful when   you re coding a document that contains   lots of those special characters  like   scripts and code fragments   it s   easier on data entry  and easier on   reading  than the corresponding entity   reference       So you can infer that the exception to   the  any old text  rule is that PCDATA   cannot include any of these unescaped   special characters  UNLESS they fall   within the scope of a CDATA marked   section

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The very main difference between PCDATA and CDATA is  PCDATA - Basically used for ELEMENTS while  CDATA - Used for Attributes of XML i e ATTLIST

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CDATA  Character DATA   It is similarly to a comment but it is part of document  i e  CDATA is a data  it is part of the document but the data can not  parsed in XML  Note  XML comment omits while parsing an XML but CDATA shows as it is   PCDATA  Parsed Character DATA   By default  everything is PCDATA  PCDATA is a data  it can be parsed in XML

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PCDATA     parsed character data  It parses all the data in an XML document   Example    lt family gt       lt mother gt mom lt  mother gt       lt father gt dad lt  father gt   lt  family gt    Here  the  lt family gt  element contains 2 more elements   lt mother gt  and  lt father gt   So it parses further to get the text of mother and father to give the text value of family as    mom dad     CDATA     unparsed character Data  This is the data that should not be parsed further in an xml document    lt family gt       lt   CDATA           lt mother gt mom lt  mother gt          lt father gt dad lt  father gt         gt   lt  family gt    Here  the text value of family will be  lt mother gt mom lt  mother gt  lt father gt dad lt  father gt

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