Subject: [Geojson] Some common ground

From: Martin Daly <[email-masked]>
Date: Thu, 26 Nov 2015 09:32:51 +0000

Among all of the previous emails we do, I think, have some common ground.

Everyone *seems* to be happy:

* for GeoJSON FeatureCollection and Feature objects to be allowed to carry additional members
* that consumers should be allowed to ignore these additional members
* that producers should be warned that additional members will be ignored by some consumers

Sadly, that is it for the common ground.

Now for the uncommon ground.

1. Sean, and others, would like these additional members to be called "extensions".

[I disagree, because I think that the term is too grand for a few additional members and confers undeserved respectability. I further think that extensions are too ambiguous without a discoverable extension description (which I don't like for other reasons, below). I think that, if we are to have true "extensions", then such mechanism is a prerequisite.]

2. Sean (and others?) would like consumer->producers to make a best effort to maintain these additional members.

[Allan and I disagree, because: 1) this is attempting to impose processing on implementations when GeoJSON is simply a format definition (Allan); 2) it is unrealistic in all but the simple case (me, with additional commentary from Martin Thomson); 3) there is no way to know which additional member is part of which extension (me, back to discoverability).]

4. Some would like additional members to be allowed on the "geometry" objects, eg to discover that the 3rd ordinate is M, not Z.

5. Jeff, and others, would like "extensions" to have some kind of discoverable description embedded in the JSON so that they are discoverable.

[(Forgive me if I've forgotten it, but I don't remember seeing a concrete proposal to this effect, although I think that some other ones have been referenced.) I agree that this is required for truly useful extensions, but don't want it because I think that it adds complexity that is not in keeping with the spirit and substance of GeoJSON as it stands.]

If we can agree on the common ground, then can we move forward with that now, and then tackle the others (ie numbers 1. to 5.) individually or in combination, as appropriate, next?

Martin