XML rule sets are sets of instructions written in a scripting language (such as JavaScript or AppleScript) that evaluate XML data and take certain actions if that data meets certain conditions. Each rule consists of at least one condition and at least one action. A rule evaluates the XML data against the conditions, and if a condition is met, then it takes the appropriate action. For example, an XML rule can specify that whenever the Paragraph element appears under the Subhead element (a condition), a specific style (an action) is applied; or that whenever the Product element (a condition) appears, a new frame is created and a product image is imported (actions). XML rules are a means of dynamically creating and formatting layouts based on XML.

For an in-depth look at using XML rule sets with InDesign, see www.adobe.com/go/learn_id_XMLrules and www.adobe.com/go/learn_id_XMLscript.