The only child element in <Classes> is <Class>. <Class> has a child element of <Item>. See Example 1 for sample code.
To facilitate organization, values for a given option may be grouped together as <Items> in a <Class>. The <Class> element can then be applied in the <Settings> and <RuleTraitsSet> elements to declare the options available for that specific option.
<Class name="boolean">
<Item value="true" stringid="boolean-true" />
<Item value="false" stringid="boolean-false" />
<Class name="color-name">
<Item value="transparent" />
<Item value="aqua" />
<Item value="black" />
<Item value="white" />
<Item value="yellow" />
Example 1: Sample Code Illustrating Child Elements, Attributes, and Values in the <Classes> Element