Am 28.08.2014 um 23:02 schrieb Xavier Noria: > On Thu, Aug 28, 2014 at 10:39 PM, Peter Wendorff > <wendo...@uni-paderborn.de> wrote: > >> No, it isn't. >> The interpretation of the database, and the meaning, restricted to the >> fact of the streets oneway-ness is the same, but no value at all does >> not say "this is no oneway street", it says nothing more than "we don't >> know if it's oneway or not". > > That is the generic interpretation of a NULL value in programming (I > am a programmer), absence of value. But your contract is that unset > implies no for streets. So there you go. Got no value? I *have* to > assume no. > > And since that's the case, the de facto usage pattern seems to be to > leave oneway unset. The database has millions of NULLs for which the > users mean an actual "no". They didn't bother, but it is NULL for no. > > And that is a consequence of the design of the data model for that > attribute. If this was 0-day of OSM and the attribute had possible > values "one-way", "two-way", "reversible", with an active default of > "two-way" preselected in UIs, then you could in practice say NULL > means unknown. +0.5, as UIs are decoupled from the data in OSM. You may write your own editor with a completely different UI, even one that doesn't know about oneway at all, so reasoning on UI preferences may help to get the best default, but not to derive rules from.
regards Peter _______________________________________________ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
