XML in a Nutshell, 3rd Edition

Attributes

XML elements can have attributes. An attribute is a name-value pair attached to the element’s start-tag. Names are separated from values by an equals sign and optional whitespace. Values are enclosed in single or double quotation marks. For example, this person element has a born attribute with the value 1912-06-23 and a died attribute with the value 1954-06-07:

<person born="1912-06-23" died="1954-06-07">
  Alan Turing
</person>

This next element is exactly the same, as far as an XML parser is concerned. It simply uses single quotes instead of double quotes, puts some extra whitespace around the equals signs, and reorders the attributes.

<person died = '1954-06-07'  born = '1912-06-23' >
  Alan Turing
</person>

The whitespace around the equals signs is purely a matter of personal aesthetics. The single quotes may be useful in cases where the attribute value itself contains a double quote. Attribute order is not significant.

Example 2-4 shows how attributes might be used to encode much of the same information given in the record-like document of Example 2-2.

Example 2-4. An XML document that describes a person using attributes

<person>
  <name first="Alan" last="Turing"/>
  <profession value="computer scientist"/>
  <profession value="mathematician"/>
  <profession value="cryptographer"/>
</person>

This raises the question of when and whether one should use child elements or attributes to hold information. This is a subject of heated debate. Some informaticians maintain that attributes ...