Subject: [Geojson] Ben Campbell's No Objection on draft-ietf-geojson-03: (with COMMENT)

From: "Ben Campbell" <[email-masked]>
Date: Wed, 01 Jun 2016 19:06:13 -0700

Ben Campbell has entered the following ballot position for
draft-ietf-geojson-03: No Objection

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COMMENT:
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For the most part, this is clear and readable. I only have a few
comments:

- I agree with Stephen's comments.

- I note several instances of 2119 "MUST" in what looks to me like
definitions, rather than requirements. For example, 'For type
"MultiPoint", the "coordinates" member MUST be an array of positions.' If
that is a choice among options, and you want to make sure implementers do
the right thing, then MUST makes sense. On the other hand, if that is
really a definitions (e.g. "... the coordinates member is an array of
positions"), then MUST is not appropriate. (For the record, I'm not sure
which case these fall into.)

- Abstract:  If I understand correctly, the document only allows a single
coordinate system. That’s stronger than “recommends”.

- 1.3: Does this document become the authoritative spec? That is, will
people need to pay attention to GJ2008 at all after this is published? if
not, then maybe "obsoletes" is the correct word. (Recognizing of course
that IETF procedure words may not quite apply here.)

- 3.1.6, 4th bullet: Why SHOULD? Can you imagine situations where it
would be reasonable to not follow the right-hand rule?

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From: Tim Schaub <[email-masked]>
Date: Wed, 1 Jun 2016 21:49:00 -0700

Thanks for the comments Ben.  My thoughts on one of them below ...

...

> would be reasonable to not follow the right-hand rule?

There has been an effort throughout the IETF process to reduce the
likelihood that GeoJSON in use today (pre-IETF GeoJSON) will not be
rejected as invalid by strict-parsers developed in the future.  The
GJ2008 document didn't discuss winding order of rings.  So while it
would be convenient for consumers if they didn't have to check the
winding order (i.e. if the spec said MUST follow the right-hand rule),
I think this is a recommendation only in hopes of improving
interoperability while retaining some backwards compatibility.

I wouldn't be opposed to making this MUST.  People will write and use
lenient parsers until old (left-hand) GeoJSON falls out of use.  With
SHOULD, we'll have mixed-handedness forever.

Tim

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From: "Ben Campbell" <[email-masked]>
Date: Thu, 02 Jun 2016 00:57:21 -0400

Thanks for the response. Comments inline:

> interoperability while retaining some backwards compatibility.

That's a reasonable motivation for a SHOULD. I'd be fine if you left it 
htat way. A few words of explanation to that effect might be useful.

> SHOULD, we'll have mixed-handedness forever.

Another possible approach would be to say that implementations of this 
spec MUST use right-hand windings, but that parsers SHOULD not reject 
left-handed windings for reasons of backwards compatibility.

Thanks!

Ben.

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From: Tim Schaub <[email-masked]>
Date: Wed, 1 Jun 2016 23:06:49 -0700

On Wed, Jun 1, 2016 at 9:57 PM, Ben Campbell <[email-masked]> wrote:
> That's a reasonable motivation for a SHOULD. I'd be fine if you left it htat
> way. A few words of explanation to that effect might be useful.
>
>>
> Another possible approach would be to say that implementations of this spec
> MUST use right-hand windings, but that parsers SHOULD not reject left-handed
> windings for reasons of backwards compatibility.

I like this idea.  Here is a pull request suggesting changes along
these lines: https://github.com/geojson/draft-geojson/pull/207

I added a note about GJ2008 compatibility.  See
https://circle-artifacts.com/gh/geojson/draft-geojson/143/artifacts/0/home/ubuntu/draft-geojson/draft.html#rfc.section.3.1.6

Curious to hear what others think.

Tim

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From: "Ben Campbell" <[email-masked]>
Date: Thu, 02 Jun 2016 08:30:04 -0400

On 2 Jun 2016, at 2:06, Tim Schaub wrote:

> spec

That looks good to me.

Thanks!

Ben.