From: Ralph Hartley (hartley_at_aic.nrl.navy.mil)
Date: Mon Feb 12 2001 - 20:14:39 CET
Received: (from mdom_at_localhost) by karto.ethz.ch (8.9.3/8.9.3/SuSE Linux 8.9.3-0.1) id UAA09731 for cavexml-outgoing; Mon, 12 Feb 2001 20:11:28 +0100 Received: from sun0.aic.nrl.navy.mil (sun0.aic.nrl.navy.mil [132.250.84.10]) by karto.ethz.ch (8.9.3/8.9.3/SuSE Linux 8.9.3-0.1) with ESMTP id UAA09727 for <cavexml_at_cartography.ch>; Mon, 12 Feb 2001 20:11:26 +0100 Received: from aic.nrl.navy.mil (pc31.aic.nrl.navy.mil [132.250.84.181]) by sun0.aic.nrl.navy.mil (8.9.3+Sun/8.9.3) with ESMTP id OAA06868 for <cavexml_at_cartography.ch>; Mon, 12 Feb 2001 14:11:27 -0500 (EST) Message-ID: <3A88361F.8000400@aic.nrl.navy.mil> Date: Mon, 12 Feb 2001 14:14:39 -0500 From: Ralph Hartley <hartley_at_aic.nrl.navy.mil> User-Agent: Mozilla/5.0 (X11; U; Linux 2.2.16-22 i686; en-US; m18) Gecko/20010124 X-Accept-Language: en To: cavexml_at_cartography.ch Subject: Re: Other areas that haven't been discussed. References: <Pine.GSO.4.05.10102111605340.26377-100000_at_cor.oz.cc.utah.edu> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-cavexml_at_karto.baug.ethz.ch Precedence: bulk Reply-To: cavexml_at_cartography.ch
John Halleck wrote:
> On Sun, 11 Feb 2001, John Halleck wrote:
>
> I don't object to your tag, I do object to what you claimed
> should be done with it. The tag has it's uses. Your comments
> about Zero Variance (formally the same as infinite weight)
> are what I do object to.
I didn't claim anything should be done with it. We are talking about a
data format, not a program. I said data marked reliability="godgiven"
("error") should be treated AS IF it had zero (infinite) variance, not
that the variance actually is zero (infinite), or that programs should
use matrixes with those weights.
> The equivalent of zero variance can, and is, obtained in the
> survey community in various ways, all of which don't involve
> actual zero variances.
And the reliability="godgiven" tag just indicates that one of them
should be used. It is not our business right now to decide which, if
any, or even to require that the method used be valid.
> If you have known bad data, then you have an idea of what
> magnitude of error you have, and it is normally weighted
> appropriately if it has to be kept in. (But, of course,
> in contexts other than Cave Surveying it would often just
> be commented out after it was reshot.)
The reliability="error" tag is just a way to comment out the values of a
set of measurements without removing the data from the file or
interfering with the processing of historical (participants, number of
trips etc.) data, or making large changes to the structure of the file.
A I said originally, a program should treat such measurements as it they
had never been done, or at least should not produce output that depends
on the measurement's values.
Even that is more proscriptive than I really want to be, but I want to
ensure that users can trust the tag to comment out measurements, and not
actually delete them, which is very unsafe ("Discard the *P* survey? I
thought you said to delete the *B* survey!").
I think we actually do agree on this, you may have read more into my
proposal than I intended.
Ralph Hartley
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