id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
18380	[RFC] Add implied tags to presets	taylor.smock	team	"I'd like to be able to get default access tags, if none exist on a highway. For example, in most countries `highway=motorway` implies `bicycle=no`, `motor_vehicle=yes`, `foot=no`, `oneway=yes`, and `surface=paved`.

So there are two methods available to get this information:
1) Hardcode it (i.e., make a java class that stores common implied information)
2) Extend the presets.xml parser to understand an `implies` tag

For example,
{{{
#!xml
        <item name=""Motorway"" icon=""presets/transport/way/way_motorway.svg"" type=""way"" preset_name_label=""true"">
            <link wiki=""Tag:highway=motorway"" />
            <space />
            <key key=""highway"" value=""motorway"" />
            <text key=""ref"" text=""Reference"" />
            <optional>
                <text key=""name"" text=""Name"" />
                <reference ref=""highway_base"" />
                <text key=""destination"" text=""Destination"" />
                <text key=""destination:ref"" text=""Destination reference"" />
                <text key=""width"" text=""Width (meters)"" />
                <combo key=""placement"" text=""Placement"" values=""left_of:1,left_of:2,left_of:3,middle_of:1,middle_of:2,middle_of:3,right_of:1,right_of:2,right_of:3,transition"" />
                <checkgroup columns=""4"">
                    <check key=""oneway"" text=""Oneway"" default=""on"" />
                    <check key=""bridge"" text=""Bridge"" disable_off=""true"" />
                    <check key=""tunnel"" text=""Tunnel"" disable_off=""true"" />
                    <check key=""cutting"" text=""Cutting"" disable_off=""true"" />
                    <check key=""embankment"" text=""Embankment"" disable_off=""true"" />
                    <check key=""lit"" text=""Lit"" />
                    <check key=""toll"" text=""Toll"" />
                </checkgroup>
            </optional>
            <preset_link preset_name=""Road Restrictions"" />
            <implies>
                <key key=""motor_vehicle"" value=""yes"" />
                <key key=""bicycle"" value=""no"" />
                <key key=""foot"" value=""no"" />
                <key key=""oneway"" value=""yes"" />
                <key key=""surface"" value=""paved"" />
            </implies>
        </item> <!-- Motorway -->
}}}

Ideally, the `implies` xml tag group would also take a country code (so `<implies country=""US,MX,GR,GB"" excludes-country=""US-FL,US-CO"">`) for country specific regions, or applying the implied tags worldwide except for specific countries. So the default scope for an `implies` block would be worldwide, unless it has a country attribute, in which case the scope decreases to those countries. If there are excludes, then those countries are excluded.
The more specific country wins (so `country=""US-FL,Earth"" excludes-country=""US""` would include the entire world, except for the US, with Florida still having the `implies` block). This does mean that there needs to be a ''special'' value for worldwide, for which I would use `Earth` instead `World` or `global` (this is mostly for future-proofing -- hopefully we will eventually have an OpenStreetMap for the Moon/Mars, but maybe we would want to use the global defaults for those anyway).

Alternatively, the `key` tags could have implied embedded in them (so `<key key=""motor_vehicle"" value=""yes"" implied=""true"" implied-countries=""US"" exclude-implied-countries=""US-FL"" />`).

Since there are some tags (`highway=motorway` as an example) where the default `implied` tags are recommended to be included due to different localities having different `implied` tags, so we can have a `recommended=yes` attribute as well, so `<implied recommended=yes>`.

I do have some proof of concept code to add the `implies` tag, but it needs significantly more work (it doesn't have include/exclude countries, check if the implied tags are recommended, and it adds the tags as if they were required tags, due to re-using the `key` tag).

This may also mean that we can write a validator rule to check if the implied tags have been added to a way (so if we have a way with the tags `highway=residential access=yes foot=yes bicycle=yes`), we can indicate that there are three unnecessary tags (`access=yes` is implied, as is `foot=yes` and `bicycle=yes`, but even if `foot` and `bicycle` weren't implied, `access=yes` also implies `foot=yes` and `bicycle=yes`)."	enhancement	closed	normal		Core		wontfix	implies, implied, tags, presets, tag, preset