The Pega Platform assembles the ruleset list during login from several sources. Afterwards, the rule resolution algorithm uses this list to determine which rules are visible and are available to be run for that requestor.
The primary source of information for your ruleset list is the application rule referenced in your access group. That application rule, in turn, usually references a second, "built-upon" application rule, which itself can reference a built-upon application.
Because there are multiple levels and sources of the rulesets in a ruleset list, your requestor session can access the "best" or "most appropriate" rule for your exact, current situation. If there are rules that only apply to your organization unit, they are included somewhere in the list. If there are — through localization — rules that cause a user screen to be presented with German-language labels and European formats for dates and currency amounts, these also are on your ruleset list. If there are rules that only apply on Fridays, or that only apply in Massachusetts, or only apply in other circumstances, these are on your list. This power and flexibility are the reasons that the ruleset list is sometimes called the situational layer cake.