[OSM-newbies] newbies Digest, Vol 37, Issue 15

[Mike Harris]

I think that Richard may have a sensible compromise here that could work 
for rights of way. Remembering that:

1. The ID / reference for a particular public right of way (PROW) 
usually applies to a single way - although occasionally to 2 or 3.
2. Any particular way almost always belongs only to a single PROW ID / 
reference (there are rare exceptions).

the bridge / tunnel analogy works for me and avoids the destruction of a 
lot of hard work while allowing the sort of revision that is being 
discussed to move most ref tags to a route that exists at a higher 
logical level. I already do this in fact for cases where there is a 
'named' or 'reference numbered' long-distance path or cycle route - 
usually involving many dozens (or hundreds) of ways. These are clearly 
'routes' as normally understood and I fully agree that in these cases it 
is the route that should carry the ref and not the numerous individual 
underlying ways. In fact it is doing this that allows me to use the ref 
tag for the PROW ID (sometimes signed and, even if not, available in the 
public domain).

The mention of bridges does remind me of another reason for supporting 
the basic proposal - with the important proviso that bridges (and PROWs? 
;-) ) are treated as having "physical" (and often signed) IDs. In 
England it is normal for bridges over canals (we have an extensive 
network of inland waterways) to carry ID numbers unique for that 
particular canal - but these bridges may also carry a highway that has a 
number reference. If the highway has a national reference number e.g. 
"A51" it would be convenient to assign this to the 'route' of the A51 
and leave a ref tag on the bridge for the number of that bridge. This 
does establish, however, a hierarchy: what if the bridge carries a PROW? 
You may want to tell me that the PROW should also be a route! (and we're 
back to my original argument and concern).

This leads me to two interim conclusions - one firm and one not:

1. If the proposed change in use of the ref= tag is to be implemented it 
MUST involve human intervention. It is too complex an issue to leave to 
a bot (even a good one, if such exist!) - if I am raising one 'grey' 
area it suggests that there may be many others out there. It is more 
difficult to make these big changes now that OSM is maturing (well 
adolescent anyway :-\ ).

2. A less drastic (?) change might be to subdivide the ref= tag (as I 
have done on occasion when faced by complexity) e.g. ref=A51 on the 
route of the vehicular highway (many ways); bridge_ref= (better? 
ref_bridge= ) on the bridge (one or very few short ways; if very 
complex, then likely already to be a relation that can be tagged 
instead); PROW_ref= on the public right of way (one or very few fairly 
short ways); ref=N99 on the cycleway route that uses the same bridge, etc.

The 'grey' area is well-exemplified by rights of way and perhaps by 
complex bridges that have not been coded as a relation - there will 
certainly be other examples. It might be a good idea to remove some / 
most of the 'grey' cases by implementing a ref_whatever= protocol (much 
easier to do for a specific set of cases - even maybe with a bot???). 
After this clean-up step it would be safer to proceed with the main 
proposal - so long as there is sufficient human intervention to avoid 
unintended destruction / loss of data from the OSM database. It's worth 
taking a little longer to get it right.

A final thought: when I was a real newbie (how long does it take not to 
be one still - a decade?) I thought relations looked difficult. They are 
not - but perhaps the wiki could be more encouraging and get people 
using them more e.g. for routes, which might reduce future problems of a 
similar kind to this one).

Cheers!

On 09/03/2010 03:54, newbies-request at openstreetmap.org wrote:
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>     1. Re: Time to retire ref= on ways? (Paul Johnson)
>     2. Fwd: Re: Re:  Time to retire ref= on ways? (Mike Harris)
>     3. Re: Fwd: Re: Re: Time to retire ref= on ways? (Zeke Farwell)
>     4. Re: [Talk-us] Fwd: Re: Re: Time to retire ref=	on	ways?
>        (Richard Welty)
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-- 
*/Mike Harris/*
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