Ron, it's not as stupid as you might think. Of course, you can use SQL to find all overlaping time periods, but for a large number of intervals, it's not going to be very efficient and it's going to take a very long time. In other words, it's not practical. Spatial option, on the other hand, uses special libraries and floating point to arrive to the target in a more optimal way. And yes, the reasoning is based on mathematics.



On 2003.10.31 15:34, Ron Rogers wrote:
Mladen,
 The information might be excellent for the "lecture on the Space and
Time Continuum" but a "black hole" will destroy all theories of anything
overlapping when they are on the same plain. Of course there has to be
an "guess work theory" about where the stuff the black hole consumes
ends up, and does it have the ability the grow at a rate proportional
the the volume it consumes?

Ron m���m


>>> [EMAIL PROTECTED] 10/31/03 02:54PM >>> I have once been asked to suggest the solution for the same problem, and I have suggested a solution which was out of this world, but completely in line with my education of a mathematician. The project was scrapped and I didn't have an opportunity to apply the solution. To start describing the solution, let me remind you that overlapping areas of space would be discovered by using spatial option. To apply the spatial option, you need to define distance function. Temporal difference does satisfy the necessary conditions for a distance function, as far as mathematics is concerned. In mathematics, there is a structure called "metric space", which is, basically, a set with a distance function. Distance function d ("metric") on set S is a function d:S x S->R which satisfies the following two conditions:


a) d(x,y)>=0 for all x,y from S. b) d(x,z)<=d(x,y)+d(y,z) for every x,y,z from S. (Cauchy inequality).


Points in time, with the difference in seconds do satisfy the above conditions, which means that you can define geometry and use spatial option. Next lesson will be about Cauchy sequences, complete metric spaces, continuous functions, contractions and Banach theorem. If Cary got away with queuing theory, why wouldn't I get away with some abstract calculus and general topology? As I've said earlier, I've never actually had an opportunity to actually apply this solution, but it still looks quite elegant to me, despite it's apparent oddity.



On 10/31/2003 01:24:37 PM, [EMAIL PROTECTED]
wrote:
> I was wondering if anyone had the need to find overlapping time
periods and how to identify them efficiently.
>
> Here is the scenario:
>
>            Elapsed minutes refer to the actual "clock" time either
spent on a given task.  Thus an activity that started at 9:00 am and
finished at 11:00 am on the same day is said to have 120 elapsed
minutes.
>            If one task overlaps another (either completely or
partially with another task), then the tasks are said to be
"multitasked".  In that case the system will store the portion of the
elapsed time that was multitasked as "elapsed multitask minutes" and the
portion of the time that was not overlapped as "elapsed single minutes".
 In addition, for the portion of time that two or more activities were
simultaneously taking place; their time will be divided by the number of
simultaneous activities and stored as "prorated multi minutes".  The sum
of Elapsed Single Minutes and Prorated Minutes will equal the actual
clock time that a vehicle was active.
>            The following example should help to illustrate these
concepts.  In the table below a list of fictitious activities for a
vehicle are shown in addition to how the time is allocated to the
various measures:
> Activity   Start Time      End Time        Elapsed
Minutes Elapsed
Multitask Minutes       Elapsed Single Minutes  Prorated Multi
Minutes Prorated Minutes        
> 1  10:00   12:00   120     60      60      25      85      
> 3  11:00   13:00   120     120     0       55      55      
> 4  11:30   13:30   120     90      30      40      70      
> 7  13:30   16:00   150     0       150     0       150     
>
Totals                  510     270     240     120     360     
> The vehicle was active from 10:00 to 16:00, a total of 6 hours (360
minutes) which is equal to the total of Prorated Minutes.
>            The vehicle performed 8 � hours (510 minutes) of work
during that 6-hour time span.  This can be arrived at by adding the
total of Elapsed Multitask Minutes (270) + the total of Elapsed Single
Minutes (240).
>
>

Mladen Gogala
Oracle DBA



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