Now, group by can be applied to any measure, but the grouping is done considering each value of the measure independently. For instance, if the grouping is applied to a time measure, it considers each different timedelta as a group. We want to extend this behaviour to allow the user to specify different groupings to apply to the grouping measure. For instance, grouping timedeltas for each 7 days. This also makes sense for data measures that refer to numeric attributes.