[OSM-dev] Implied Tags

Frederik Ramm frederik at remote.org
Tue Apr 12 20:14:09 BST 2011


Hi,

Christian Vetter wrote:
> And the implied tags noted in the wiki pages?

Like anything else in the Wiki, these are just put there by some people 
who thought it might make sense; there is no guarantee whatsover that 
most people even know, much less make use of them.

To the best of my knowledge there's no editor support for implied tags, 
i.e. when editing you will not see what you have just "implied" - for 
example, JOSM will not automatically draw one-way arrows onto something 
you have tagged highway=motorway.

> So what would be your advice? Just ignore implied tags? They seem to
> be used in many cases ( e.g. barrier vs barrier=bollard ) and I want
> to avoid "fuzzy" parsing.

I don't think there will ever be a true, fixed set of implications, but 
there may be a growing community consensus of implications for one 
specific purpose. (I could imagine that implications for rendering would 
be different from implications for routing, say.)

My advice would be to make up a set of implications that makes sense for 
your purpose and make sure that every user of your software knows about 
it. Perhaps even put it in a config file or a wiki page; it might even 
happen that others start using it. But I would always start from the 
bottom up ("this is what *I* am doing right now, if anything is wrong 
about that, let's talk") rather than try to do something from the top 
down ("let's all find a consensus about implied tags now so that I can 
then build the one true rule into my application").

Bye
Frederik

-- 
Frederik Ramm  ##  eMail frederik at remote.org  ##  N49°00'09" E008°23'33"



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