[Tagging] Discussion about Multivalued Keys

moltonel 3x Combo moltonel at gmail.com
Thu Jan 28 13:18:52 UTC 2016

On 27/01/2016, Colin Smale <colin.smale at xs4all.nl> wrote:
> On 2016-01-27 22:54, moltonel 3x Combo wrote:
>> Concerning foo_1 vs foo[1] vs foo:1, I this the last one can be safely
>> thrown to the idea bin (despite being used by seamarks) because ':'
>> clashes with namespacing, which is firmly established. foo[1] looks
>> better than foo_1 to my programer eyes, but is has no technical
>> advantage (?) and I suspect that most people will find foo_1 more
>> pleasing, it's also one less character to type, less annoying to parse
>> with a regexp, and much more established in taginfo.
> Would you feel any different about your foo:1 example if it were written
> foo%1, avoiding any clash with namespacing?

I don't really care wether it's _1, %1 or [1], except that the first
one is already popular. But

> By the way, I am trying to maintain the distinction between the "suffix
> notation" where the index value is actually the final part of the key
> segment, and the "hierarchical/seamark" notation where the index value
> is a separate segment of the full key string.

As far as I'm aware, the "suffix notation" has always meant "suffix
within a namespace", not "suffix at the very end of the key". We
already have a significant number of "*name_1:*" keys in the db, for

> Maybe we should look at some technical use cases, like "in a navigation
> map creator, find all the categories for a POI" or "find the per-lane
> destination (and destination:ref and turn-lane stuff) information so I
> can construct a simulated road sign". Some will be done with a
> programming language, others may naturally tend towards SQL.
>> Concerning using '.' as a separator instead of ':', I don; t see what
>> it brings us, beside familiarity to users of some programing languages
>> (but change language and sudenly ':' becomes more familiar).
> Sometimes using a familiar character (such as the ":" here) with new
> semantics can lead to confusion. There comes a point when it is better
> to make a clean break so there is no confusion. Whether it is a colon or
> a dot or some other character is "detail" really.

Yes, but in the "lane[1].destination=Paris" example, you use '.' for
something (namespacing) that we've always happily used ':' before. I
don't see a need for the change, my best guess was "it looks more
familiar to users of some programming languages" but IMHO it's not
worth the confusion it'll bring to most people.

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