Path: utzoo!attcan!uunet!dev!dgis!jkrueger
From: jkrueger@dgis.dtic.dla.mil (Jon)
Newsgroups: comp.databases
Subject: Re: More on image databases
Message-ID: <749@dgis.dtic.dla.mil>
Date: 6 Feb 90 16:55:06 GMT
References: <15498@orstcs.CS.ORST.EDU>
Organization: Defense Technical Information Center (DTIC), Alexandria VA
Lines: 50

curt3028@oce.orst.edu (Curt Vandetta) writes:

>  I'm more than convinced that I will need to migrate to an object
>  oriented model to keep the images in the database themselves

Be less than convinced.  You need user-defined data types as first
class objects.  You don't need inheritance, message passing,
cheap instantiation of new objects.

>  hope to do (someday), is have the database setup in such a way that
>  the end-user can do querys on say, pixel values inside of an image.
>  query like "Give me all of the tiles e (where e is say the tile that
>  has the San Francisco Bay in it) where the average temperature for the
>  bay is above 55 degrees"

	select i.name, i.date, i.technican from image i where
		avg_temperature(i.tile) > fahr_to_kelvin(55)

Now the bad news: no existing commercial RDBMS can do this.
Some are close, but I won't give plugs: ask your local sales
critter.  If he says no, kill him.  This will encourage
right thinking in vendors :-)

Also note that first class support includes access methods
appropriate to the data type, in this case 2d, else all
such queries will be exhaustive table scans and response
time will increase linearly with table size.

>  this was just an example, the query could be on say
>  pixel 10245, so it would "every tile with pixel 10245 greater than
>  134 (a byte value that represents 55 degrees)".

Same bad news, but same good news: nothing in the relational
model stops you from:

	select i.name, i.date, i.technican from image i where
		pixel(i.tile, 10245) > 134

But wouldn't you rather:

	select i.name, i.date, i.technican from image i where
		avg_temperature(coastline(i.tile)) > avg_temperature(standard)

???

-- Jon
-- 
Jonathan Krueger    jkrueger@dtic.dla.mil   uunet!dgis!jkrueger
The Philip Morris Companies, Inc: without question the strongest
and best argument for an anti-flag-waving amendment.