On Wed, Dec 3, 2008 at 11:05 AM, Roan Kattouw roan.kattouw@home.nl wrote:
Without addressing Commons in particular, having an efficient way to get pages in the intersection of multiple categories would allow wikis to delete a category such as [[Category:Deceased Presidents of the United States]] and replace it by, say, [[Intersection:Deceased Presidents of the United States]], which would list all articles in [[Category:Deceased people]] and [[Category:Presidents of the United States]]. My extension alone doesn't make that possible, but it makes implementing such a feature considerably easier.
[snip]
We've had tools like this on toolserver before, with decent performance and the ability to be embedded into commons via cross site JS hacks, and been told in no uncertain terms that the community policy is "do not over categorize; things should be placed in the fewest and most specific categories possible". On commons there are quite a few contributors who spend all of their time converting the set of categories on an image to the one or two most specific categories.
Please pardon Dschwen's frustration: because it seems like people are constantly waving their arms and saying that there will be some wonderful technical solution right around the corner for the problems created by the current categorization approach (never mind that some of them, such as the extreme semantic drift, are unsolvable with a technical solution).
For commons, and a lesser degree other projects, the limiting factor in the usability of an intersection tool is less the lack of one and more the insistence of the userbase of using categories in a manner which is generally incompatible with them.
For the purposes of MediaWiki these factors are not important, I suppose, but it does explain the sceptical response.