my 2¢ On 18.12.2012 15:29, Denny Vrandečić wrote: > Thanks for the input so far. Here are a few explicit questions that I have: > > * Time: right now the data model assumes that the precision is given on the > level "decade / year / month" etc., which means you can enter a date of birth > like 1435 or May 1918. But is this sufficient? We cannot enter a value like > 2nd-5th century AD (we could enter 1st millenium AD, which would be a loss of > precision).
We need a system for expressing accuracy anyway, for empirical values (measurements). I suggest to apply the same concepts (maybe even the same code) to dates. We'll need to be able to express accuracy in several ways, e.g. as standard deviation, +/-% range, gamma distribution, etc. Simply specifying a range as "+/- 3600 seconds" to indicate a precision level in the hour range would fit in, I think. > * Geo: the model assumes latitude, longitude and altitude, and defines > altitude > as over mean sea level (simplified). Is altitude at all useful? Should it be > removed from Geolocation and be moved instead to a property called "height" or > "altitude" which is dealt with outside of the geolocation? I'd include altitude, but make it optional (while long/lat are mandatory). Expressing accuracy here can and should work similarly to "normal" (1D) measurements and dates, usually given as a +/- range. > * Units are currently planned to be defined on the property page (as it is > done > in SMW). So you say that the height is measured in Meter which corresponds > to 3.28084 feet, etc. Wikidata would allow to defined linear translations > within > the wiki and can thus be done by the community. This makes everything a bit > more > complicated -- one could also imagine to define all dimensions and units in > PHP > and then have the properties reference the dimensions. Since there are only a > few hundred units and dimensions, this could be viable. I don't like the idea of defining units on the property pages at all. For one thing, it means a lot of overhead introducing new units, or at least standardizing the names of units (should that be "ton" or "metric ton"?...). This makes it hard to compare values of different properties (say, comparing average life expectancy to maximum life span or some such). At least the base units (SI units) should be implemented in software. Derived units could be defined on the wiki, but on their own pages, not for each property. > (Non-linear transformations -- most notoriously temperature -- will get its > own > implementation anyway) A far more tricky conversion would be between different reference globes for coordinates. But that wouldn't be handled as a "unit", I suppose. -- daniel -- Daniel Kinzler, Softwarearchitekt Wikimedia Deutschland - Gesellschaft zur Förderung Freien Wissens e. V. _______________________________________________ Wikidata-l mailing list Wikidata-l@lists.wikimedia.org https://lists.wikimedia.org/mailman/listinfo/wikidata-l
