XML Attributes and Elements

XML Attributes

XML elements can have attributes, just like HTML.

Attributes provide additional information about an element.

XML Attributes

In HTML, attributes provide additional information about elements:

<img src="screen.gif">

<a href="example.asp">

Attributes often provide information that is not a part of the data. 

In the example below, the file type is irrelevant to the data, but can be important to the software that wants to manipulate the element:

<file type="gif">screen.gif</file>

XML Attributes Must be Quoted

Attribute values must always be quoted.

 Either single or double quotes can be used. For a person's sex, the person element can be written like this:

<person sex="female">

or like this:

<person sex='female'>

If the attribute value itself contains double quotes you can use single quotes, like in this example:

<gangster name='Adam "Shotgun" Zuckenberg'>

or you can use character entities:

<gangster name="Adam &quot;Shotgun&quot; Zuckenberg">

XML Elements vs. Attributes

Take a look at these examples:

<person sex="female">
  <firstname>Angelina</firstname>
  <lastname>Will Smith</lastname>
</person>

<person>
  <sex>female</sex>
  <firstname>Angelina</firstname>
  <lastname>Will Smith</lastname>
</person>

In the first example sex is an attribute. In the last, sex is an element. Both examples provide the same information.

There are no rules about when to use attributes or when to use elements. Attributes are handy in HTML. 

In XML my advice is to avoid them. 

Use elements instead.

Best Way Practised

The following three XML documents contain exactly the same information:

A date attribute is used in the first example:

<note date="10/01/2008">
  <to>Tom</to>
  <from>Jerry</from>
  <heading>Reminder</heading>
  <body>Don't forget Birthday Party this weekend!</body>
</note>

A date element is used in the second example:

<note>
  <date>10/01/2008</date>
  <to>Tom</to>
  <from>Jerry</from>
  <heading>Reminder</heading>
  <body>Don't forget Birthday Party this weekend!</body>
</note>

An expanded date element is used in the third: (THIS IS MY FAVORITE):

<note>
  <date>
    <day>10</day>
    <month>01</month>
    <year>2008</year>
  </date>
  <to>Tom</to>
  <from>Jerry</from>
  <heading>Reminder</heading>
  <body>Don't forget Birthday Party this weekend!</body>
</note>