​​​​​​​​XML Rules​


​​​​​​​​​Yes, even though the language is quite free in it’s structure and syntax, but what did you expect… you could write ​
​anything anywhere?!! Sorry, but that’s not the case…But still, the developers have lent us with quite a very few ​
​rules. So, the language still remains to be quite easy. Congrats.!! this is what i said to myself when I myself was ​
​learning it.​
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​​​​​​​Rule 1: All opening tags should have a closing tag​
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​​​​​A closing tag is defined by placing a ‘/’ before the tag name of the opening tag.​
​For example…​
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    ​​​​​<Ayush>—–</Ayush>​​​​​​​​​
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    ​​​​​<India>——-</India>​​​​​​​​​
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​​​​​All opening tags are strictly required to have a matching closing tag.​
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​​​​​​​Rule 2: XML tags are case sensitive​
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​​​​​Take care when defining tags as the tag names are case sensitive i.e. ‘Ayush’ and ‘ayush’ are two totally different ​
​things.​
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​​​​​​​Rule 3: XML tags should be properly nested​
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​​​​​It means that if tag A started in tag B then it should end before tag B.​
​For example:​
​<aa><bb> Testing tags </aa></bb>———–illegal​
​<aa><bb> Testing tags </bb></aa>———–legal​
​Though this rule is not valid in HTML. In HTML, both of the above code lines would be valid. (just the tags need to ​
​be changed to valid ones)​
​This is a very important rule as it preserves the tree structure of the data we are inputting in the XML file.​
​You should take care to preserve the tree structure of the data.​
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​​​​​​​Rule 4: All XML files should contain a root element​
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​​​​​The first tag of a XML file is known as the root element​
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​​​​​​​Rule 5: XML attributes must be quoted​
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​​​​​All tags of XML can have properties known as attributes. They are defined with the tag name.​
​For example​
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    ​​​​​<Ayush age=”19″>​​​​​​​​​
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​​​​​Here Ayush is the tag name and age is his attribute. You should always remember to put the attribute value in ​
​quotes.​
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​​​​​​​Rule 6:Avoid using special characters of XML and use Entity Reference​
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​​​​​Some characters have a special meaning in XML.​
​For example, If we use a character like ‘<‘ in our XML element, the XML parser will take it as a starting of a new ​
​element and generate an error.​
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    ​​​​​<check>if age < 18 </check>​​​​​​​​​
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​​​​​It will generate an XML error:​
​To avoid this error, replace the “<” character with an entity reference:​
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​There are 5 predefined entity references in XML:​

​&lt;​ ​<​ ​less than​
​&gt;​ ​>​ ​greater than​
​&amp;​ ​&​ ​ampersand ​
​&apos;​ ​’​ ​apostrophe​
​&quot;​ ​”​ ​quotation mark​

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​Note: Only the characters “<” and “&” are strictly illegal in XML. The greater than character is legal, but it is a ​
​good habit to replace it.​
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​​​​​​​Rule 7: Adding comments in XML is an easy task​
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​​​​​It does not seem to be a rule but make sure that no tag of yours turns out to be interpreted as a comment the ​
​XML parser. You can add comments to XML by using syntax:​
​<!—add comments—->​
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​​​​​​​Rule 8: XML saves your white spaces​
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​​​​​Unlike HTML, XML preserves the white spaces added by you in it’s elements or other things.​
​For Example:​
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    ​​​​​Hello, my name is       Ayush​​​​​​​​​
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    ​​​​​HTML:​​​​​​​​ Hello, my name is Ayush​​​​​​​​​
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    ​​​​​XML:​​​​​​​​ Hello, my name is       Ayush​​​​​​​​​
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​​​​​​​How to name your XML tags?​​​​​​​​​

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  • ​​​​​Names can contain letters, numbers and characters​​​​​​​​​
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  • ​​​​​They should not start with a number or punctuation character​​​​​​​​​
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  • ​​​​​Don’t start the names by XML, xml etc​​​​​​​​​
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  • ​​​​​They should not contain spaces​​​​​​​​​
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  • ​​​​​No words​​​​​​​​ are reserved, so you can use any word​
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