[OSM-dev] Suggestion about design of OSM data structure (take out segment component)
80n
80n80n at gmail.com
Thu Jul 26 19:06:30 BST 2007
On 7/26/07, Frederik Ramm <frederik at remote.org> wrote:
>
> Hi,
>
> > Your argument is not valid because you are assuming that branching ways
> > (Y-shaped) are 2 ways direction but they may be one way direction in the
> > real life!
>
> That doesn't make my argument any less valid for those ways that are not
> oneways. Your picture (2) is what I had in mind; you are right in saying
> that if the main road is another type of road it needs to be split
> anyway, but we often have a residential road with residential branches,
> so they're all the same type.
>
> It is desirable to split these into individual ways, even today, because
> it makes things easier for renderers and so on. And it is possible. All
> I'm saying is that it will require a lot of manual work. Even if you
> could prove that, in theory, such ways couldn't exist because they
> violate some rule, I can tell you from practice that they do.
>
> About areas with holes:
> > Without segments, I still can use simple way to model area with hole.
> > For example: I have 11 nodes. Node: 1, 2, 3, 4, 10, 11 form the outer
> > ring clockwise and nodes: 5, 6, 7, 8, 9 form inner ring anticlockwise.
> > Two rings joined at node 4 and 5.
>
> That's a bad way to do it. Imagine you have an area drawn with contours
> (for example, lakes sometimes have a darker blue contour and a light
> blue fill) - the contour would run straight through your lake from 4 to 5!
>
> > 1. When you design data structure for map, you need to save any space as
> > much as possible because map data are very huge.
>
> Amount of data hasn't been a problem until now. If it were a problem,
> then we would probably stop using free-form keys and values for our tags
> and replace them with integers, and we would stop tagging every single
> node, segment, and way with a "created_by" tag ;-)
>
> > 2. Data structure must be simple enough so that other program can
> > process your data.
>
> I agree that ditching segments would make things easier. Almost
> everybody agrees that that's the case. We're currently more or less
> waiting for someone to program the changes necessary on all levels -
> API/database, renderers, editors, etc.
>
> > I hope osm foundation will consider my arguments and take out the
> > segment component from planet.osm xml file.
>
> Whether or not the OSM Foundation - which, technically, isn't the boss
> in this project but let us assume for a moment they were - approves the
> idea of removing segments will depend very much on whether the
> appropriate code exists at that time. This project is not normally run
> top-down (decision makers decide, then programmers write code) but the
> other way round. Or, to say it more bluntly: It's not going to happen
> unless someone writes the code.
Speaking for the OSM Foundation - it doesn't get involved in technical
questions at all - that's all driven by the community.
The purpose and role of the Foundation is to support the project financially
and act as a legal entity where one is necessary.
80n
But I'd welcome someone to do it.
>
> Bye
> Frederik
>
> --
> Frederik Ramm ## eMail frederik at remote.org ## N49°00.09' E008°23.33'
>
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