Subject: [Geopriv] PIDF-LO needs a "derived from another form" method

From: "Brian Rosen" <[email-masked]>
Date: Wed, 20 Jul 2005 14:32:36 -0400

In draft-ietf-geopriv-pidf-lo-03, there is a "method" parameter that
describes how the location was determined.  Although I don't like the whole
idea, it seems clear that many folks want to allow transformations between
civic and geo, and sending both forms in one tuple.  If we do that, then the
method should be "derived" or something like it, indicating that the
location data was not determined originally by that method, but some
transformation has been applied to it.  This needs another registered value.

I would like text that says, "If location is provided with method 'derived',
the original version of the data, with the method actually used to determine
it SHOULD also be provided".

Brian

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From: Andrew Newton <[email-masked]>
Date: Wed, 20 Jul 2005 16:42:58 -0400

> it SHOULD also be provided".

Who is doing the transformation?  Or more importantly, when is it  
being done?  If it happens before the DHCP exchange, then I don't see  
how this adds any more information than the currently listed method  
of "DHCP".  In addition, since there can only be one <method>  
element, changing it from "DHCP" or "802.11" or whatever to "derived"  
would throw away the fact that the location came from DHCP, 802.11,  
or whatever... wouldn't it?

What is the gaol behind doing this?  I just don't see how the  
"derived" token provides useful information.  If I see "DHCP" in the  
<method> element, I can go look at the various standardized methods  
for DHCP location.  If I see "derived", how does that help me.   
Derived from what?  Using what methods?

-andy

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From: "Brian Rosen" <[email-masked]>
Date: Wed, 20 Jul 2005 17:04:16 -0400

It's being done by some entity before the UA sends it.
It probably won't happen with DHCP, at least without some other service.  It
probably will happen with the "Layer 7" mechanisms people are talking about.

It only is applicable when you have another form of the data.  Say the data
originates as a civic (method=manual), but someone thinking he is going to
be helpful also has available a geocoding engine and gives you his version
of what that civic is like as a geo.  It's not GPS, it's derived by
geocoding the civic.  There are folks who think this is a very good idea,
and they plan to send both the civic and the geo along.  We need a way to
know which is the original, and which is the transformed version.

The same could be done to a method=A-GPS.  It could reverse geocode and give
you a derived civic.

The suggested text says "never send just the transformed value, always send
the original at least, and if you want to send the transformed value, okay,
but mark it as derived from the other one".

-----Original Message-----
From: Andrew Newton [mailto:[email-masked]] 
Sent: Wednesday, July 20, 2005 4:43 PM
To: Brian Rosen
Cc: 'GEOPRIV'
Subject: Re: [Geopriv] PIDF-LO needs a "derived from another form" method

-andy