[OSM-talk] Extended tagging schema - my thoughts

Peter Wendorff wendorff at uni-paderborn.de
Fri Aug 10 10:05:37 BST 2012

Am 09.08.2012 17:51, schrieb Rob Nickerson:
> Hi all,
> One of the issues raised with the extended conditions tag schema was 
> the use of variable values in the key part of the tag. For example 
> maxspeed:wet = 80 is in the form constant:variable=variable. This has 
> been deemed to break the basic tagging rules.
> Can I therefore give alternative suggestions:
>   *  maxspeed=120; 80?wet; 60?wet+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
> This is off the form constant=condition value; condition value. Using 
> this existing schema, the maxspeed example becomes:
>   *  maxspeed=120; wet 80; wet+hgv 60
> 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 would "require" to always set the unconditioned maxspeed at first 
before the ";", so a fallback may be implemented easily if an 
application don't want to interpret the conditions.

one open question would be how to deal with units in this combination: 
mph, m/h, km/h, and the usual errors mp/h, kmh, and so on, but I think 
even that should be relatively easy to do, as the numbers are always the 
last token before the separator (;), and if there's anything between 
number and separator, that could be interpreted as a unit.


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