Re: A neutral challenge.

Bob Badour wrote:

>When I attended Chris Date's UCLA Extensions course last year, it occured to
>me that subtypes and type generators go a long way to expressing many
>recurring events as intervals. If THIRD_THURSDAY is a subtype of THURSDAY is
>a subtype of DAY, one might express an event on the third thursday of every
>month using an interval type INTERVAL_THIRD_THURSDAY.
>
>The gaps one must cross are that INTERVAL_THIRD_THURSDAY is neither a
>subtype of INTERVAL_THURSDAY nor of INTERVAL_DAY and that the calendar
>probably schedules events at a finer granularity than days. One would need a
>way of recasting interval types so that the third thursdays in one type of
>interval become days in a different type of interval, and then combine those
>days with a time of day to construct finer granularity schedules.
>
>Obviously declaring types for THIRD_THURSAY and SECOND_WEDNESDAY etc. would
>be tedious, so I think type generators for various date and time
>granularities probably make sense too.
>
I think using types for this purpose is a slight overkill. It would be easy to add a 'day of week' and
a 'day of week in month' column into materialised calendar and just use them in selection criterias.

regards,
Lauri Received on Thu Jun 26 2003 - 07:30:19 CEST