Message-ID: <014301c3d4f2$ce2bffb0$9100053d@winxp>
From: "Chris Travers" <chris@travelamericas.com>
To: "Kumar" <sgnerd@yahoo.com.sg>, <josh@agliodbs.com>,
	"Peter Eisentraut" <peter_e@gmx.net>, "psql" <pgsql-sql@postgresql.org>
References: <00a501c3d41b$2dc9a0e0$7502a8c0@hdsc.com>
	<200401061956.57063.peter_e@gmx.net>
	<200401061413.12096.josh@agliodbs.com>
	<001701c3d4e4$62fc4dc0$7502a8c0@hdsc.com>
Subject: Re: Calendar Scripts - Quite a complex one
Date: Wed, 7 Jan 2004 14:49:28 +0700
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Hi all;

If I understand Kumar's post correctly, he is having some question relating
to the issue of even recurrance.  I would highly suggest reading the
ICalendar RFC (RFC 2445) as it has some interesting ideas on the subject.
HERMES (my app with appointment/calendar functionality) doesn't yet support
appointment recurrance, and I have not formalized my approach to this.
However, here is the general approach I have been looking at:

1: Have a separate table of recurrance rules (1:1 with appointments) or have
a recurrance datatype.

2: Build some functions to calculate dates and times when the appointment
would recurr.  You can also have a "Recur Until" field so you can limit your
searches this way.

3:  Use a view to find recurring appointments on any given day.

This avoids a very nasty problem in the prepopulation approach-- that of a
cancelled recurring meeting.  How do you cancel ALL appropriate instances of
the meeting while leaving those that occured in the past available for
records?

Kumar-- if you are working with PHP, I would be happy to work with you in
this endevor so that the same functionality can exist in my open source
(GPL'd) application.  I think that the source for this would likely be one
of those things that might be best LGPL'd if added to my app.

Best Wishes,
Chris Travers

----- Original Message -----
From: "Kumar" <sgnerd@yahoo.com.sg>
To: <josh@agliodbs.com>; "Peter Eisentraut" <peter_e@gmx.net>; "psql"
<pgsql-sql@postgresql.org>
Sent: Wednesday, January 07, 2004 1:06 PM
Subject: Re: [SQL] Calendar Scripts - Quite a complex one


> Hi,
>
> The complexity comes while scheduling the appointments. Let us say, I have
> scheduled so many meetings in my calendar of various schedules like daily,
3
> days once, weekly, bi weekly. monthly, bi monthly, etc.
>
> While I open the calendar for end of this year (say Dec 2004), I need to
> show those meetings in my calendar, but I have data until Jan 2004.
>
> What is the best way to show it. Populating the records from Jan 2004 to
Dec
> 2004 in the pgsql function and display it in the calendar, or just write a
> query to generate temporary records only for that Dec 2004 and not storing
> them at the database.
>
> Please shed some idea.
>
> Regards
> Kumar
>
> ----- Original Message -----
> From: "Josh Berkus" <josh@agliodbs.com>
> To: "Peter Eisentraut" <peter_e@gmx.net>; "Kumar" <sgnerd@yahoo.com.sg>;
> "psql" <pgsql-sql@postgresql.org>
> Sent: Wednesday, January 07, 2004 3:43 AM
> Subject: Re: [SQL] Calendar Scripts - Quite a complex one
>
>
> Peter,
>
> > You can probably lift out the complete calendar functionality from an
> > existing groupware solution, say, www.egroupware.org.  I'm not sure
> > whether it's practical to do the calendar things in the database, since
> > you will also need a significant amount of intelligence in the client
> > to display reasonable calendar graphics, for instance.
>
> But all of the appointments, holidays, etc can and should be stored in the
> database, and by using function programming one can automate generating
all
> of the raw data for the calendar graphics.   We do this with our legal
> calendaring app.
>
> --
> -Josh Berkus
>  Aglio Database Solutions
>  San Francisco
>
>
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