Snodgrass is also the author of an excellent book on the subject, available
at a bookstore near your browser.
| "Henry Poras" <[EMAIL PROTECTED]>
Sent by: [EMAIL PROTECTED] 11/03/2003 01:49 PM
|
To: Multiple recipients of list ORACLE-L <[EMAIL PROTECTED]> cc: Subject: RE: Finding overlapping time periods - suggestions please |
Also check out
http://www.cs.auc.dk/research/DP/tdb/TimeCenter/TimeCenterPublications/TR-28
by Richard Snodgrass.
Henry
-----Original Message-----
Mladen Gogala
Sent: Friday, October 31, 2003 6:09 PM
To: Multiple recipients of list ORACLE-L
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 mª¿ªm
>
>
> >>> [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 ½ 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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> --
> Author: Mladen Gogala
> INET: [EMAIL PROTECTED]
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--
Mladen Gogala
Oracle DBA
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