XML Attribute Values Must be Quoted

XML Attribute Values Must be Quoted

XML elements can have attributes in name/value pairs just like in HTML.

In XML, the attribute values must always be quoted.

Study the two XML documents below. The first one is incorrect, the second is correct:
<note date=12/11/2007>
  <to>Tove</to>
  <from>Jani</from>
</note>

<note date="12/11/2007">
  <to>Tove</to>
  <from>Jani</from>
</note>

The error in the first document is that the date attribute in the note element is not quoted.

Entity References

Some characters have a special meaning in XML.

If you place a character like "<" inside an XML element, it will generate an error because the parser interprets it as the start of a new element.

This will generate an XML error:
<message>if salary < 1000 then</message>

To avoid this error, replace the "<" character with an entity reference:
<message>if salary &lt; 1000 then</message>

There are 5 predefined entity references in XML:
&lt;     <     less than
&gt;     >     greater than
&amp;     &     ampersand
&apos;     '     apostrophe
&quot;     "     quotation mark

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.

Comments in XML

The syntax for writing comments in XML is similar to that of HTML.

<!-- This is a comment -->

White-space is Preserved in XML

HTML truncates multiple white-space characters to one single white-space:
HTML:     Hello           Tove
Output:     Hello Tove

With XML, the white-space in a document is not truncated.

XML Stores New Line as LF

In Windows applications, a new line is normally stored as a pair of characters: carriage return (CR) and line feed (LF). In Unix applications, a new line is normally stored as an LF character. Macintosh applications also use an LF to store a new line.

XML stores a new line as LF.