NYCPHP Meetup

[inforequest]

Sorry this isn't really about php code, but I am working at a conceptual
level here.. and since you said you have free time on your hands, mabe
you'll enjoy experimenting :-) I worked with some programmers on
events-based databases a few times, and have programmed my own in numerical
C and a small one in PHP. I am not a professional programmer, and I get
very annoyed very easily when dealing with the nuances of date/time as
implemented by MySQL or another not-really-standard system.

The event data really is start TIME and DURATION (plus venueID, title,
etc). After that, you have data redundancy (end date is just start time +
duration, second day is just start time - time of day plus 24 hours, etc).
In actuality, START TIME is realy just OFFSET FROM BASELINE too pick your
baseline.. Julian zero, etc).

The math associated with scheduling is done with matrices (linear algebra,
or matrix math). That is very, very fast, and allows you to do clever
things to get what you want. So I like to store start START TIME and
DURATION, and if I want to store derivitives I can certainly do that for
practical reasons, but I need to handle them as I would any non-normalized
data. Any serious scheduling math will be done on the time matrix which
only includes ON or OFF for time segements in the time space (if you
resolve to theminute, then minutes are ON or OFF). Make the segments any
size you like for flexibility, and re-segment anytme you like for utility,
down to your preset max resolution/smallest increment (usually minutes).

The user input should be as friendly as possible -- that's a UI job. For
functionality, the system can provide the UI with a mask on the absolute
time frame defined by START TIME and END=START+DURATION. 

So an event is Dec 1 - Dec 4 2004. Really it is Dec 1 8am tru Dec 4 4pm,
and that means *really* it is START 12/1/04 09:00 DURATION 103 hours. For
minute segments, that's 6180 minutes.

So the user blocks out 12/2/04 9-10 am via your UI, and the system assigns
minutes 1440 - 1500 (one hour) to that "event".

You may be surprised at how flexible your back end becomes if you work with
the data in this manner, and abstract it to the UI for appearances and
utility for the user. Wanna change the event to another month? Update the
START TIME. Wanna look for the least-booked 2 hour slot to plan an ad-hoc
session? Search for a local minimum for offset from start as ordinate, and
some sort of attendance estimate on the abscissa. Want to reschedule
concurrent sessions to better accommodate the demand for a popular sesson?
Same story... "slide" a bock representing session duration on X vs.
estimated attendance on Y along a similar time/estimatedattendance scale
for the entire event sans that session, adding the Y values together
("slide along" and "add" etc are basic linear algebra operations, simply
expressed via matrix operations and super fast). Then seek a minimum.

Want a plot of hallway activity? You can get clever taking derivitives
(very fast algo) of the time/atendance blocks on that same scale... dy/dt
spikes at the edges/transitions between sessions, proportional to
attendance. Smooth it via a window function and you get an interesting
approxmation of hallway traffic -- perhaps that helps schedule housekeeping
visits, vendor breaks, etc. I hope you get the idea....

Not everybody will do their back end calculations with numerical algos, or
get excited about the possibilities for data analysis like this, but when
things get complex that is what the engine is doing anyway (or trying to
do). 

If you get comfortable separating data from presentation, and abstracting
to the UI for utility, abstracting to the DB for platform independence,
etc..  then you might appreciate the gains from further separating EVENT
ATTRIBUTES from the data/time constraints of MySQL/PHP or whatever as well.

-=john andrews


Original Message:
-----------------
From: leam-at-reuel.net |nyphp dev/internal group use|
...
Date: Tue, 30 Nov 2004 06:45:37 -0500
To: talk at lists.nyphp.org
Subject: [nycphp-talk] I need a date...sorta...

p.s. For once I'm not in a rush. I've set no promised date for this so I
have time to think it through. If there's a function or web page I should
read, point me to it!


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