You can compose rule sets from already defined rules or sorting directives. To include an already-defined rule set or sorting directive in your rule set, you can use the src attribute with the <ruleset>, <rule>, and <sortby> tags. The syntax for the three tags in this form is:

<ruleset src={path}></ruleset>
<rule src={path}></rule>
<sortby src={path}></sortby>

where the path is the Nucleus path of the rule, rule set, or sorting directives to be included.

Note that if you include a rule set using the <ruleset src="..."> tag, the tag must be contained by an includes tag. Also, when you include a rule set with the <ruleset src="..."> tag, only the rules from that rule set are included; any sorting directives in the included rule set are ignored. You can, of course, include them using the <sortby src="..."> tag.