[Tagging] Extended tagging schema - my thoughts

Eckhart Wörner ewoerner at kde.org
Fri Aug 10 03:00:26 BST 2012

Hi Rob,

Am Donnerstag, 9. August 2012, 17:33:59 schrieb Rob Nickerson:
> Can I therefore give alternative suggestions:
>   *  maxspeed=120; 80?wet; 60?wet+hgv

Ask a few mappers not participating in this discussion what this key/value combination is supposed to express, and I'll bet most of them will have problems telling you the correct meaning; e.g. the first time I read this, I interpreted wet+hgv as "wet or hgv".

> Here '?' can be interpreted as 'if' and '+' as 'and'. Many alternatives can
> be proposed using alternate symbols (or none at all). In fact, it is
> already in use:
>   *  opening_hours=Mo-Sa 10:00-20:00; Tu off

I'd be careful using the opening_hours syntax as an analogy, e.g. what is
maxspeed = 80?wet;120
supposed to mean?

> Advantages: Easy to reduce back to the basic condition, editors can
> implement this in a fancy GUI; expandable, can use bots to analyse/fix

I'm not sure what "easy to reduce back to the basic condition" means. However, all the other advantages you list exist for almost any tagging scheme proposed so far.

Here are some disadvantages of merging everything into a single value:
- readability and ease of manual editing suffers
- you lose backward compatibility
- you don't integrate widely used conditions like forward, hgv, …
- you run into the (real) risk of exceeding the 255 byte limit imposed on values


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