How to Create a Xml File

Creating well formed XML Documents 

1.The <?xml> tag and the root element
  ➢ It is the first element
  ➢ It specifies the version
  ➢ Only one root element

2.Opening and Closing tag
  ➢ <name> </name>

3.Empty element
  ➢ <bookname></bookname> or <bookname/>

4. Entities

1.Character entities- &entity; (&gt;, &lt; , &apos;, &quot; , &amp;)

2.Binary entities- <!ENTITY city SYSTEM “delhi.html” NDATA html>
   1.!ENTITY  - Keyword
   2.City – Entity name
   3.System – DTD type
   4.“delhi.html” - Actual contents
   5.NDATA – Non-XML(Binary)
   6.Html – how to interpret

3.Text entities- <!ENTITY country “india”>       
(name)   (content)

XML Declaration

● <?xml 

  version="version_number"  

  encoding="encoding_declaration” 

  standalone="standalone_status" 

  ?>

● At first position 

● Version: default 1.0 

● Encoding attribute: encoding of characters that are permitted in the document

● Standalone attribute: value-no if any external markup declaration content of : 

– Attribute with default values 

– Entities(other than &amp; &lt; ) 

– Element type with element content,if white space occurs directly

XML naming rules

● Element name should be consistent 

● Begin with a letter or _ followed by any number of letters, numbers, hyphens, colon and _ 

● Case sensitive 

● Can not contain space 

● Numbers must not have prefix of xml eg:W3C, xmlname can not be used 

● Can not use name begin with 'x' 

● Brevity tag names: <queue> rather than <q> 

● Maintain standard naming conventions and quoting(BookStore)

XML naming rules

● : colon is used to demarcate namespace prefixes from the actual name. 

● Avoid usage of double punctuation combination(.,)) 

● XML 1.0 doesnt specify a character limit in XML names, many parsers will have problems with constructs longer than 256 characters.

Element content

● It is handled in one of the 2 ways 

– Parsed Character Data(PCDATA): it is examined by the XML parser to discover XML content embedded within it. 

– Character Data (CDATA): it is delimited by the special syntax <![CDATA[...]]> and is not processes by the parser.

PCDATA-Parsed Character Data

● All textual data is processes by default. 

● Special characters need to be handled carefully to prevent confusion in the processor. 

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

Ampersand: &amp;  

& Single quote: &apos;  ' 

Greater than: &gt;  > 

Less than: &lt;  

< Double quote: &quot;  “

● “;” is needed to differentiate between markup characters and text characters. 

● Single and double qoute uses apostrophes. 

● When there are lots of them within document, CDATA is used.

CDATA – Character Data

● <![CDATA[ ... .. ] ] > 

● CDATA is not parsed and is treated as it is. 

● CDATA can not be nested. 

● It will retian spaces. 

● Useful for embedding other languages within XML(& use &#38) – HTML document – Xml document – Java scrtipt or any other

CDATA Example

● The following markup code shows example of CDATA. Here, each character written inside the CDATA section is ignored by the parser. 

<script> 

<![CDATA[   

  <message> Welcome to TutorialsPoint </message> 

]] >

 </script > 

● In the above syntax, everything between <message> and </message> is treated as character data and not as markup.

Element tag- Rules

● End tag is identified by / eg: <color> </color> 

● Elements may contain attributes within the start tag 

  – Eg: <book isbn=”324”></book> 

● Empty elements contain no child elements of text. 

● Eg <record key=”111”> </record> can be represented as <record key=”111” /> or <record /> 

  – Space is required before /

Element attributes-Rules

● Attribute provide extra info of tag(key info) 

● Used to attach information to elements 

● Consists of name=”value”, name is a legal XML name 

● Placed in start tag 

● May have several attributes 

● <title type=”sec1” number=”1”>XML intro</title>

Comments

● For clarification inside actual element tags 

● It may not be nested. 

● Use whenever it is needed. Not much 

● <!-- -->

Well formed versed Valid

● Well-formes = follows all rules 

● Valid= both well formed and adheres rules 

● well formed XML: 

  – Consists of XML elements that are nested within another 

  – Has a unique root element  

  – Follows naming conventions 

  – Follows rules for quoting attributes 

  – Has all special characters properly escaped. 

● Valid Xml document has an associated vocabulary defined by DTD or XML schema