Updates to MML

[yhahn]

Let's coordinate on revamping MML to make tilelive-mapnik breath a little easier. Discussing with @springmeyer and @tmcw it looks like we have two options

1. Expand the mml format to allow for additional information (with sensible defaults).
2. Create a new format that "wraps" mml that tilelive-mapnik can use.

My thought is to expand MML to contain the following tilejson keys:

// existing MML keys
srs
Layer
Stylesheet

// tilejson keys
name
description
version
attribution
legend
minzoom
maxzoom
bounds
center
formatter
scheme

We also need to figure out what to do with two key pieces of information

format (png, jpeg, etc.)
interactivity (layer, keyname)

I think format is basically a tilelive-mapnik specific key. interactivity on the other hand I think should make its way back into Mapnik XML -- maybe as a property/flag of the <Layer> structure or so.

[yhahn]

I'm going to move on this by updating TileMill bones to write the above ^^ to the project mml file for now. If we decide to go with a new format I would imagine it will not be too different except

• We'll need a new extension (not .mml)
• We'll need that file to contain some reference to the .mml file to use (filepath, url?)
• We'll need another layer of localization for that external reference (yeay)

[springmeyer]

@yhahn - sounds good, this is certainly a good way to move forward as we get squared away on all the props needed. One more coming down the pipe will be a render time 'resolution' (https://github.com/mapbox/tilemill/issues/403). The implications of this for tiles are not clear (because you'd have > 256 px tiles) but the idea its used not just for high res single prints but for better looking mobile tiles like on iphones with the retina display.

[kkaefer]

We also have some keys capitalized. This is because the JSON originated from XML where the keys were uppercase. We can't translate the JSON to XML directly anyway, so we might just as well switch to lowercase keys for the sake of consistency.

As for localization, I see the natural place for this in tilelive-mapnik. It's currently happening in carto which makes no sense at all. Ideally, we'd translate the carto styles without localizing anything, then write a generic localizer that processes mapnik XML stylesheets.

[kkaefer]

Update on the localization: this is now handled in the millstone module, which is called by tilelive-mapnik

[miccolis]

I'm looking at standardizing the name of the mml file in TileMill projects to project.mml. For TileMill projects this makes it dead simple to copy a project creates a standard entry poing. I'm looking into what effect such a change would have on tilelive-mapnik.

My question here is this; as this is an older ticket, is anything still in motion here?

[springmeyer]

nothing still in motion here as far as I know. We added further keys to mml (rather than inventing a new format) and that's been working just fine.

[springmeyer]

closing.