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[mkgmap-dev] Style rules and 'generated' tags

From Steve Ratcliffe steve at parabola.demon.co.uk on Tue Jul 7 16:44:13 BST 2009


> So what will happen with this example.
> highway=* {set tag_a=yes}
> tag_a!=yes {set tag_b=yes}
> tag_a=yes [0x01 resolution 20]
> tag_b=yes [0x02 resolution 20]
> highway=* [0x03 resolution 20]
> Will all highways be converted to 0x01, 0x02 or 0x03?

My guess was 0x01.  But it turns out that I was wrong :)  Actually
it is not a valid style because you can't have tag_a!=yes all by itself.

If it were tag_a=yes then the answer would still be 0x01
because that is the first rule with a definition that matches.

It seems that the action rules are being used a lot more than I thought
going some way beyond what they were designed for.  We need to look at what
the actions are being used for.  I get the impression that a lot of it is
to normalize inconsistent tagging, so perhaps we need a separate stage
where that is done explicitly.


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