The last section in the Rules tab of your data garden are the Event based rules.   

Any rules that are created in this section are executed upon any record if your record meets the criteria that is set within the rule. With an interval of approximately 4 hours, the system will automatically check every record in your project (regardless of the status) to see if it matches the criteria you have set. If a record matches, the rule will be executed. Due to the fact that this rule type is executed in a set frequency, you are not dependent on a trigger like when you are using the Creating records or Mutating records sections. So you are able to modify any record, even historical data.

An example

If a respondent has filled out the KPI question, but has not finished the rest of the questionnaire, the results are not included in your dashboard. By default, only completed records are included. But you would like to include the KPI results of these incomplete records. 

To accomplish this, you can create a rule that looks for records that have an answered KPI question, but no Completed Date. If the records meets all these criteria, set the records to status complete.

You could even add a waiting period, by adding a condition that the sys_updated date must be older than a week, to ensure the respondent has enough time to complete the questionnaire.

In short, by using the rules in the Event Based section you are able to apply rules to every record in your database. Simply define the changes you want to make within a rule, and within no more than 4 hours the updates are applied to any record in your database that meets the conditions you have set.