A category of database items. These items represent the amount of time during a collection interval spent doing a particular activity. Interval-based items are updated through out the collection interval and timing is restarted at the end of the interval. Interval-based items should only be used to show amount of time in an interval for an activity or to calculate percentages of time spent in an interval. Interval-based items should not be used to calculate averages (such as average hold time).