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Summary
To contrast attributes with elements, here are two examples of student record data that are traditionally stored in a database. The first example primarily uses elements (element-centric) to store data values. The second example primarily uses attributes (attribute-centric).
Elements vs. Attributes with Database Oriented Data
To contrast attributes with elements, here are two examples of student record data that are traditionally stored in a database. The first example primarily uses elements (element-centric) to store data values. The second example primarily uses attributes (attribute-centric).
Element-centric
<students>
<student id=2456>
<name>Jim Smith</name>
<grade>10</grade>
<gpa>3.5</gpa>
</student>
<student id=2457>
<name>Mary Jones</name>
<grade>12</grade>
<gpa>3.4</gpa>
</student>
:
<students>
Attribute-centric
<students>
<student id=2456 name=Jim Smith grade=10 gpa=3.5 />
<student id=2457 name=Mary Jones grade=12 gpa=3.4 />
:
</students>
With relational database data, the choice between attributes and elements does not appear all that important. Only unique keys, which establish a link between elements (such as student id), must be attributes to facilitate the linking of records (that is, other elements). With the attribute-centric approach, each element is a record, and each attribute is a field.
Although either approach works, it is generally recommended to use elements instead of attributes. For instance, to distinguish between first and last name, the element-centric approach can be changed to:
<name>
<first>Jim</first>
<last>Smith</first>
</name>
The attribute-centric approach is less favorable because the attribute must be split into two attributes.
<student ... firstname=Jim lastname=Smith .../>
Only the element-centric approach is compatible with XSL.
Element-centric XSL transform:
<xsl:value-of select=name/>
The transform above results in Jim Smith in both element-centric approaches, but the attribute-centric approach requires two different transforms.
Attribute-centric XSL transform for one attribute:
<xsl:value-of select=@name/>
Attribute-centric XSL transform for two attributes:
<xsl:value-of select=@firstname/> <xsl:value-of select=@lastname/>
Excepts from XML Unlocks Information: How XML Accommodates Human-Authored Content
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