Please find my comment on core lines below.
Am 28.06.2010 19:54, Michał Borsuk:
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*ISSUE RAISED:
* change to the way more complex lines are mapped, that is the
introduction of tags or roles instead of nested collections*
Present status: For lines with variants, each variant needs a separate
relation
Problems:
* Nested relations are difficult to impossible to manage in potlatch,
* They are difficult to understand
* Creating a variant requires the entire route to be duplicated:
impossible in potlatch
* Extending or rerouting such lines can be hell
* High risk of introducing a mess by inexperienced users (I think). I
actually think my proposal is more error-resistant.
* It's time-consuming! It's easy to duplicate a line once one knows
JOSM, but how much time does it take to get JOSM running, from
downloading to having results? A lot.
*Proposed change: introduction of a "core line", that is shared by all
variants in all directions, and having the branches or exceptions in
one direction tagged appropriately. Core line would have no tags,
branch lines would be tagged arbitrarily. *
Result: lower consistency of the data entered, but much less time
needed to enter and manage lines. The "mess" can be easily dealt with
by server-side software presenting data to users. If one wants a route
from one's side branch of a line, one looks down the tagged branch up
to the main branch, and then up to the stop needed. Nothing hard to
implement. It's the 21st century, I believe that we don't have to rely
on simple parsers that take nothing else but point-to-point connections.
How would you enter this core line? It would be a relation with the ways
and stops of the course again. So you would need the core line be a
member of the branches and exception relations again. Probably I haven't
fully understood how you would see your core lines respresented in the
OSM data model.
Pozdrowienia,
Claudius
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