XML - Extensible Markup Language
we hav seen HTML previously ...it is a markup language...i.e. we specify the textual content
of the document
as well as we specify how the textual content should be structured or shuld be displayed on
the screen...but there's a problem with HTML
in HTML set of tags are limited by the definition of HTML i.e. the tag set and tag semantics
are predefined and fixed...
XML specifies neither a tag set nor semantics...it provides facility to define tags...XML is a
meta-language for describing markup languages...
XML is defined by the following specifications :
1.Extensible Markup Language (XML) 1.0 -- defines the syntax of XML
2.XML Pointer Language (XPointer) and XML Linking Language (XLink) -- defines a
standard way to represent link between resources
3.Extensible Style Language (XSL) --defines the standard stylesheet language for XML...
------------------------------------------------------------- XML Document consists of
-------------------------------------------------------------
1. Prolog :
first structural element present in the XML document...usually divided into an XML
declaration and DTD - Data type declaration [option]
examples :
<?xml version = "1.0" encoding = "UTF-8"?> {UTF-8 is some kind of encoding rules}
<?xml version = "1.0"?>
2. Elements :
most common form of markup...XML elements must contain a start tag and a matching end
tag prefixed by a slash...
e.g. <city>Kharagpur</city> ...empty elements can be written as <city/> instead of both tags
without contents...XML is case sensitive
Element Naming Convention in XML : mustt start with a underscore or letter...can contain
letters,digits,hyphens,underscores and periods
Attributes :
Attributes are attached to elements...name value pairs that occur under start tag after the
element name...
must begin with a letter or underscore...must not contain any white spaces...
Entity Reference :
they are used to reference data taht is not directly in the structure...can be internal or
external...
