The InTimeInterval of single flow slice
We probably want all the small flow slices to be the length of their time slice (because currently the flow slice may overflow from its time slice, which is wrong). Therefore, we get rid of their started field and change the iterator of the time slice to produce some wrappers that reference both the time slice and the flow slice. The values would come from the flow slice, but the intervals from the time slice.
This probably needs some changes in the query processing.