[OSM-talk] Recording completeness

[Chris Morley]

At SOTM07 it was apparent that there are many organizations ready to use 
OSM data when it is complete enough.  The need for measures of "quality" 
was also raised. So perhaps now is the time to set up a framework where 
"completeness" can be recorded.  It would provide not only a measure of 
progress, but also be an incentive to mappers to literally go the extra 
mile. As has been previously noted, well-defined "complete" areas (IOM, 
IOW) are a valuable publicity tool.

There are many possible ways of recording completeness and there have 
been intermittent discussion of this in the past. (Being aware of all 
previous discussion on a list like this is not easy.) But here is one 
possiblity, for discussion.

Completeness boundaries would be ways in the the main data base so that 
contributors can push the boundaries on a day to day basis. A boundary 
of completeness would always be a closed area with the completed area to 
the right of segment direction (like coastlines). This means that the 
meaning of a boundary would be understandable even when only a small 
part of it was visible. It would also mean that the areas couldn't be 
tiled (segment directions wrong) but that it would be easy to merge 
them, which is what is really needed.

Obviously, there are various levels of completeness, and it would be 
necessary to tag the boundary with a description of this, for example 
boundary="complete" completeness="public roads". It would be better to 
use standard text descriptions like "major roads" or "public roads" for 
this,  rather than a numerical index. Areas of different completeness 
could be nested and could share nodes/segments in part. There would be 
guidelines on what the various categories meant. So maybe "public roads" 
could mean that >97% of public roads in an area had ways and were named 
where appropriate, with enough information for basic routing for cars - 
oneway, etc. I think this is the category that should receive the most 
attention.

I'm not clear whether each area would need to be a single way (necessary 
for local rendering?) or whether they could be conveniently split, like 
coastlines, and viewed via a low zoom custom rendering in 
informationfreeway.org.

Eventually it will be necessary for areas to have "guardians" or 
"mentors" to maintain quality, but this currently happens informally, 
which is good enough for now.

Chris