And thanks for the use cases. This helps a lot with thinking about this. On Thu, Aug 31, 2017, 16:31 Denny Vrandečić <[email protected]> wrote:
> The reason why we save the actual value with more digits than the > precision (and why we keep the precision as an explicit value at all) is > because the value could be entered and displayed either as decimal digits > or in minutes and seconds. So internally one would save 20' as 0.333333333, > but the precision is still just 2. This allows to roundtrip. > > I hope that makes any sense? > > Yes, that means that using the values for comparison without taking the > prevision into account will fail. > > I don't think comparison and other operators were ever specified for the > datetypes. This has bitten us before, and I think it would be valuable to > do. And that would resolve these issues, and some others. > > Would there be people interested in doing that? I sure would love to get > it right. > > On Thu, Aug 31, 2017, 16:17 Stas Malyshev <[email protected]> wrote: > >> Hi! >> >> > I am not sure I understand the issue and what the suggestion is to solve >> > it. If we decide to arbitrarily reduce the possible range for the >> >> Well, there are actually several issues right now. >> >> 1. Our RDF output produces coordinates with more digits that specified >> precision of the actual value. >> 2. Our precision values as specified in wikibase:geoPrecision seem to >> make little sense. >> 3. We may represent the same coordinates for objects located in the same >> place as different ones because of precision values being kinda chaotic. >> 4. We may have different data from other databases because our >> coordinate is over-precise. >> >> (1) is probably easiest to fix. (2) is a bit harder, and I am still not >> sure how wikibase:geoPrecision is used, if at all. >> (3) and (4) are less important, but it would be nice to improve, and >> maybe they will be mostly fixed once (1) and (2) are fixed. But before >> approaching the fix, I wanted to understand what are expectations from >> precision and if there can or should be some limits there. Technically, >> it doesn't matter too much - except that some formulae for distances do >> not work well for high precisions because of limited accuracy of 64-bit >> double, but there are ways around it. So technically we can keep 9 >> digits or however many we need, if we wanted to. I just wanted to see if >> we should. >> >> -- >> Stas Malyshev >> [email protected] >> >
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