User talk:Andy Dingley/Archive 2009 November

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Category talk:Grayback class submarines

I seldom handle the categories of vehicles or weapons, hence may be unfamiliar with the usual practices outside my own narrow main field. Mostly I photograph, categorize and geotag the local landscape, but one of these submarines is part of the local landscape, which led me to climb its category tree and install an interwiki link. Many categories are not well aligned between Commons and the language Wikipedias, and no reason for them to be so aligned. Where practical, however, I like to establish such links. In the rare case where a Wikipedia Image category corresponds fairly exactly, that's the target. Second choice is an en topic cat, and last resort goes to a directly relevant article.

For some cases, but not according to any general rule, I link to an en Wikipedia article (and in rare cases another language) at the top of the Commons cat also, or instead. Far as I know, there isn't an established guideline or ordinary way of doing these things, so we are still playing by ear. Perhaps there ought to be a cat wrangling Project Page or Help Page or something, or perhaps all the above does exist and I just haven't looked for it properly. Jim.henderson (talk) 14:28, 17 November 2009 (UTC)

Category:Model steam locomotives

See COM:OVERCAT - basically, if A is in CAT:B, and B is in CAT:C, don't put A directly into C. Therefore, as Category:Model steam locomotives is a member of Category:Steam locomotives, which is itself a member of Category:Live steam, it shouldn't go in directly. Also, although it isn't the case for the two images in the category at present, models of steam locomotives may not themselves be live steam - for example File:Hornby dublo 8f.jpg. Therefore I do not think this category is appropriate. Tivedshambo (talk) 11:30, 28 November 2009 (UTC)

First of all, that's guidance rather than dogma.

Secondly, it's mostly about images and we're dealing with categories here (this does make a difference).

Thirdly (and least controversially) let's assume that Category:Model steam locomotives is purely for "models of steam locomotives also powered by steam", and incorrect members of that need re-categorization anyway.

It's a fair point that transitive categories shouldn't be duplicated, by re-stating the grandparent onto the child. However in some cases, there is some functional relation between the grandparent and the parent, and also between the grandparent and the child. This exists as a relation between the two categories directly: it's not merely an implication from the transitive relationship. Here, "live steam" is as relevant to the categorization of "steam locomotives" as it is to "steam engines" (and "steam boats", "stationary steam engines" et al.). It's of particular relevance when the supercategory is both a parent cat, and a category of content in its own right (we might choose to empty "steam engines" in favour of "stationary steam engines" and the other more-specific categories, but at present it includes both the cats and general content images that aren't otherwise categorized).

There is as much reason to categorize Model steam locomotives into Live steam as there is for Steam locomotives or Model steam engines, and for exactly the same reason. This isn't reduced by it also being implied elsewhere, as it could be for some other transitive categories.

Why do we categorize? It's not to imply that the cat-member is-a whatever the cat describes in a particularly strong sense. We have plenty of counter-examples to support this: images categorized where they are useful or illustrative and thus relevant to a category, where there's no suggestion of a claim that "the core feature of this image is-a <foo>" (the strong claim for categorization). If we did start to need to express this strong is-a property, then we'd be best doing it with OWL-based annotation on the image pages (DBpedia is getting close to needing this already). Our existing practice for categorization has already ruled out the "strong definitions only" option.

One of our major use cases for categorization is as a navigation structure for browsing. Why would a reader be browsing Live steam? What would they expect to be seeing when they do so? In that sense, Model steam locomotives is one of the major goals of the search, at least as important as Model steam engines.

There's also the question of categories rather than images. Our major reason for wishing to avoid re-stating implied transitive categories is to avoid bloating the supercategories with "everything". However that's an issue for the many images, much less of a problem for the relatively few categories. Andy Dingley (talk) 14:57, 30 November 2009 (UTC)

To be honest, Andy, this is such a trivial thing that I really cannot be bothered to get into an edit war about it, which is why I didn't make a second revert. My only concern is the issue of differentiating between live steam models of steam locos, and non-steam models. Perhaps a second category is required for the latter types, though I'm not sure what to call this. Any suggestions? Tivedshambo (talk) 16:46, 30 November 2009 (UTC)