Subject: RE: [Geopriv] draft-thomson-geopriv-geo-shape-00

From: "Abbott, Nadine B" <[email-masked]>
Date: Mon, 6 Mar 2006 08:50:08 -0500

I think I need a forest guide to help me sort the forest from the
trees....

Political geographical boundaries, e.g., counties, nations, etc. are
likely to be described in the routing databases for location-based
services.  Passing around in a PIDF-LO all the geo-coordinate
information necessary to describe such a polygon, just to describe the
presence/location of an individual user, seems like a waste of signaling
resources to me, when such a location can so economically be described
with a civic location object. 

I understood the motivation for providing polygon information in a
PIDF-LO to be primarily to describe the estimated coverage of a wireless
access point or to describe building or campus locations when more
accurate  information to pinpoint the location of a user could not be
provided.  
If applications arise that require providing more detailed boundaries
that are not easily represented by civic location shorthand, then we'd
want the specification to allow for that. But I wouldn't think it would
be the norm? Some implementation guidance seems appropriate for the
applications that we do know about. 

I think that the requirements of LUMP/LOST to describe boundary
information for serving areas are entirely different from the
requirements for the PIDF-LO which is intended to describe the location
of an individual.
I don't think we'd want to impose the needs of the location-based
routing information protocols on supporting location information for
users in SIP message bodies, myself.  If advice about using GML is
needed for other applications, then perhaps there is a need for a BCP or
something to provide that advice, rather than morphing PIDF-LO to
support all applications.
Are there not any concerns about the size of PIDF-LO in the message body
that would be required to support civic geographic boundaries in terms
of vertices in the thousands?

Respectfully,
Nadine Abbott

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On
Behalf Of Henning Schulzrinne
Sent: Sunday, March 05, 2006 9:57 AM
To: Winterbottom, James
Cc: [email-masked]; James M. Polk
Subject: Re: [Geopriv] draft-thomson-geopriv-geo-shape-00

There is a big difference between giving implementation advice and
artificially restricting functionality. As noted, PIDF-LO has broad
applicability, with many applications that we can't predict, most of
which won't involve emergency calls or 3G.

There is a somewhat separate aspect: The description in these drafts is
also taken as advice on how to use GML within other IETF documents. (My
remark was actually triggered by the attempt of a grad student of mine
to integrate the polygon description into the LUMP/ LoST test
implementation of ours, to describe regions.) There, the 16- point limit
makes absolutely no sense.

On Mar 5, 2006, at 3:01 AM, Winterbottom, James wrote:

> I would actually suggest in that case that we use the 16 point bound 
> as a limitation for Location routing applications also. I think that 
> trying to perform arbitrary spatial lookups based on a polygon 
> containing many 100s of points is hardly going to be something that we

> want to try an do in real or near real time. I might also question the

> need for someone to need to express their personal presence in such a 
> way, but that is a different discussion completely.
>

_______________________________________________
Geopriv mailing list
[email-masked]
https://www1.ietf.org/mailman/listinfo/geopriv

_______________________________________________
Geopriv mailing list
[email-masked]
https://www1.ietf.org/mailman/listinfo/geopriv

---

From: Henning Schulzrinne <[email-masked]>
Date: Mon, 06 Mar 2006 15:48:05 -0500

Nadine,

I think the topic at hand has been resolved, but there's probably a 
slightly larger issue that may well lead to other misunderstandings in 
the future. Thus, maybe the PDIF/PDIF drafts can make this a bit 
clearer. I think there are three somewhat separable issues; from your 
note, I think we're largely in agreement:

(1) PIDF-LO will be used to convey information about people or objects 
in fairly generic environments. We can't really anticipate what kind of 
objects these will be, and they may have odd shapes. (Picture a 
presentity that represents some game region or avatar in a new 
coordinate system.)

(2) PIDF-LO will be used for some well-defined, fairly narrowly-scoped 
applications, such as the body of an INVITE heading to a PSAP. That is 
unlikely to require to describe the borders of Manhattan. It probably 
makes sense to restrict what PSAPS need to deal with; the BCP for 
emergency call device behavior seems like a good place to collect such 
information.

(3) Some of the same GML elements used in PIDF-LO will be used as region 
descriptions in LUMP/LoST, for example. Another likely application are 
privacy policy documents. It makes sense to have a single way to 
describe polygons in XML in IETF protocols, not half a dozen, unless 
there's a strong need for generic GIS functionality. I don't think we 
need additional I-Ds for that, just appropriate language in the PDIF 
(spelling intentional, echoing the draft spelling typo...) and geo-shape 
drafts.

Does this make sense?

Henning