Private-use messages

[e-n-f]

Creators and users of vector tiles should be able to include private messages within tiles, layers, and features, by mutual agreement. Other software that doesn't know how to interpret these messages should pass them through as opaque blobs to the extent that is possible.

Something like:

message private {
    required string = 1;
    extensions 20 to max;
}

and then in each of tile, layer, and feature,

    repeated private = 6;

(or some other number).

One of the options for value could also be an object of this type if there is a need for opaque feature attributes.

The string in the private message would be the URL for the specification for the private message type. There is no need for software to actually download a file from the URL; it just serves to distinguish one type of private message from another.