[Openstreetmap-dev] Data Primatives & schema

Andy Robinson Andy_J_Robinson at blueyonder.co.uk
Tue Dec 20 19:26:46 GMT 2005


Following on from my stab last month on a schema, I took on board the
comments and decided on a different tack. Matt had taken a look at an OSM
XML schema so I'm kind of feeding off that but focussing on the user end of
things rather than how the database stores and communicates with users.

First off I wanted to go back to the data primitives. No intention
whatsoever in trying to change the principal database structure in any way
but rather wanting to consolidate some of the recent discussion and make
some minor revisions of the wiki page.

The definitions on the wiki are not entirely explicit, thus I produced the
following to try and be a little more explicit. 


NODE: Any point on, under or attached to the earth.

Line SEGMENT: An association of two separate NODEs

WAY: An association of one or more line SEGMENTS

ZONE: An association of three or more NODEs where the first and last NODEs
have the same uid.

Just three questions:

1. Are the definitions sufficiently explicit?
2. Are the statements correct?
3. Any comments on the nomenclature change of Street to WAY and Area to ZONE

Initially I called the WAY (formerly Street) a POLYLINE, however a polyline
would be made up of nodes and not line segments. Since I could not see any
reason why we would have to have polylines with no breaks I think the
original idea of it being made up from line SEGMENTs is better. Its also a
more logical way of mapping since on the whole its better to lay down the
nodes and segments before establishing that the whole is Baker Street. "Way"
was used instead of "Track" because of the similarity with gps tracks which
was pointed out.

Cheers

Andy







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