[OSM-talk] Changed highway=*_link meaning?!

[Ed Avis]

Isn't this tagging redundant?  If a link road leads from a primary to a
secondary, or whatever, this can be seen by looking at the tags for the two
roads it connects.  In principle there is no need to duplicate the information.

In practice a renderer such as Mapnik may not allow you to write such complex
rules, and doing so would complicate its code.  As a blue-sky idea, we could
have 'virtual tags' which are generated by the server automatically when you
download a section of map.  As well as taking care of the different kinds of
link road, these could also provide 'is_in', 'leading_to' and 'dead_end' for
streets, and uphill/downhill for slopes (based on the layer of the endpoints).
Some simple query language would define such virtual tags and new ones could be
added if an application finds them useful.

-- 
Ed Avis <eda at waniasset.com>