[RFC] Feature Proposal - Replace `*:signed` suffix key with `is_signed:*` prefix key

[Minh_Nguyen (Minh Nguyễn)]

From the proposal:

Software generally assumes that the suffix of the name key is a ISO 639 language code such as “en”, “de” etc.

Software should assume that only a valid IETF BCP 47 language tag (such as an ISO 639 language code) can represent a language subkey. signed is not a valid language tag. In case it helps, here’s a regular expression for matching name subkeys in Java, and here are tests to prove that it works.

@lonvia

Nominatim has always operated under the assumption that name:* tags contain some kind of name and are therefore all indexable for search. name:signed has joined a blacklist together with other problematic tags like name:wikipedia and name:etymology.

The root of the issue is that subkeys of name serve two different purposes:

1. This is another name in another context: name:en, name:genitive, name:left. Sometimes this is expressed as a different base key: alt_name, official_name, sorting_name.
2. This key refines name with something you should know about the value of that tag: name:pronunciation, name:etymology, name:signed. Sometimes this is expressed as a prefix: source:name. In the specific case of name:pronunciation, technically we should’ve instead chosen e.g. name:en-fonipa for better standards compliance, but I suspect Nominatim would’ve had to special-case that anyways.

Which usage is worse? I think that’s mostly a subjective, aesthetic decision, since OSM keys are too inconsistent for there to be very much automated logic around their structure. The latter usage exists because the data model does not formally support associating a key with an array of values or an array of key-value tables. (If it did, this thread wouldn’t have stretched for over 200 comments and counting.)

While understandable, it was not the most forward-thinking decision to make language tags direct subkeys of name:*. It essentially assumed that no two- or three-letter English word would reasonably be a standard subkey. Naturally, to became a popular key, and Valhalla’s developers riffed off it by promoting destination:to. But this is not the name of the destination in the Tongan language; that would have to be destination:lang:to.

StreetComplete apparently regrets its promotion of *:signed because it affects not only name:* but also various other keys that could come with their own standard subkeys. But if the goal is to make key construction more predictable, there would be a long way to go. This table of standard key slots has an additional row for not only *:signed but also *:wikidata.

Meanwhile, I can never remember if psv:lanes or lanes:psv is the one with the vertical bars in it.