From: P A Hill & E V Goodall (goodhill_at_xmission.com)
Date: Fri Jul 19 2002 - 17:57:44 CEST
Return-Path: <owner-cavexml-outgoing_at_ethz.ch> Delivered-To: cavexml-archive_at_cartography.ch Received: from localhost (localhost [127.0.0.1]) by karmail.ethz.ch (Postfix on SuSE eMail Server 2.0) with ESMTP id 3AFE814AB0 for <cavexml-outgoing_at_ethz.ch>; Fri, 19 Jul 2002 18:07:29 +0200 (CEST) Received: by karmail.ethz.ch (Postfix on SuSE eMail Server 2.0, from userid 28) id 1848D14A7E; Fri, 19 Jul 2002 18:07:27 +0200 (CEST) Delivered-To: cavexml-loopcheck_at_ethz.ch Received: from localhost (localhost [127.0.0.1]) by karmail.ethz.ch (Postfix on SuSE eMail Server 2.0) with ESMTP id 196FB14AB0 for <cavexml-loopcheck_at_ethz.ch>; Fri, 19 Jul 2002 18:07:26 +0200 (CEST) Received: by karmail.ethz.ch (Postfix on SuSE eMail Server 2.0, from userid 96) id EA1E414A46; Fri, 19 Jul 2002 18:07:23 +0200 (CEST) Delivered-To: cavexml_at_cartography.ch Received: from localhost (localhost [127.0.0.1]) by karmail.ethz.ch (Postfix on SuSE eMail Server 2.0) with ESMTP id 9BCA114AB0 for <cavexml_at_cartography.ch>; Fri, 19 Jul 2002 18:07:23 +0200 (CEST) Received: from mgr1.xmission.com (mgr1.xmission.com [198.60.22.201]) by karmail.ethz.ch (Postfix on SuSE eMail Server 2.0) with ESMTP id 0712E7EA9 for <cavexml_at_cartography.ch>; Fri, 19 Jul 2002 18:07:20 +0200 (CEST) Received: from [198.60.22.200] (helo=mail.xmission.com) by mgr1.xmission.com with esmtp (Exim 3.35 #1) id 17Va1R-0007CQ-00 for cavexml_at_cartography.ch; Fri, 19 Jul 2002 09:50:25 -0600 Received: from goodhill.dsl.xmission.com ([198.60.114.17] helo=xmission.com) by mail.xmission.com with esmtp (Exim 3.22 #1) id 17Va1R-0002LK-00 for cavexml_at_cartography.ch; Fri, 19 Jul 2002 09:50:25 -0600 Message-ID: <3D3836F8.9020109@xmission.com> Date: Fri, 19 Jul 2002 09:57:44 -0600 From: P A Hill & E V Goodall <goodhill_at_xmission.com> User-Agent: Mozilla/5.0 (Windows; U; Win98; en-US; rv:0.9.4.1) Gecko/20020314 Netscape6/6.2.2 X-Accept-Language: en-us To: cavexml_at_cartography.ch Subject: Re: Data model : branches and nodes References: <5.1.0.14.1.20020719160945.01d513c0_at_popa.melbpc.org.au> <003a01c22f22$70191240$c7ab07c3_at_argussoft.ru> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Loop: cavexml Sender: owner-cavexml_at_karmail.ethz.ch Precedence: bulk Reply-To: cavexml_at_cartography.ch X-Virus-Scanned: by AMaViS perl-11
Alexander Nickolsky wrote:
> Another issue is that introducing these entities causes data duplication,
> and this is not a good practice.
Not necessarily. The entity mentioned so far might map to something as
simple as an optional attribute attached to a point. For example a
intersection or node (i.e. where one or more survey shots come together sharing
the same known point in the cave) might just be an attribute of a point element
<point id="..." x="..." y="..." z="..." node=123>
where the optional node attribute brings together all points labeled with the
same node ID into a set meaning that they are all topologically the same point
in the system and physically supposed to be the same point in the cave. That is
just an example.
I see that this is the second time in two days someone has immediately
assumed that an entity mentioned had to have its own complex data structure.
Somehow for the purpose of the design we've got to get everyone to
think in terms that an entity MIGHT not have its own structure, it is just
something that is useful to standardize into the data format for those who use
such things.
> For example a single Branch could replace a whole string
> of non-bifurcating Legs/Shots.
If the goal is to adjust the points so that loops all close upon themselves,
it is only loops that matter. A tree of bifurcating passages contributes nothing
to such efforts, regardless of how many branches and sub-branches there are.
It is more than just non-bifurcating that are the odd folks out. It is the
difference between the USA usage of the street sign that says "Dead End" and the
less common sign that is sometimes used to mark a small neighborhood with only
one way in and out, the "No Outlet" sign.
[Warning: British usage differs]
http://www.geneseecountyparks.org/images/wpe125.jpg
http://members.aol.com/rmoeuradot/200x200/warn/W14-2p.gif
In the case the loop mathematics things to identify are either:
1. nodes which are part of loops,
OR
2. all points including nodes which are part of loops,
or
3. legs (and thus all points shots and nodes) which are
parts of loops.
In each case we might choose to identify that which is not
in the set instead of that which is.
More to think about,
-Paul
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