Jon Lang wrote: > Conversely, the relationship between an article on Urban Planning and > a City category is _not_ an "is-a" relationship: Urban Planning is not > a city. But while it's not a valid class/instance relationship, it > _is_ a valid category/article relationship. You've voiced distaste > for this sort of relationship, and have suggested alternatives that > conform to your preference of only using "is-a" relationships; but > that doesn't change the fact that it's still a valid relationship.
Very good points. For many reasons, I don't think it is defensible to use page/category in the same way as instance/class. This is an old debate that flares up and goes away without resolution. A very big problem is that many pages are already pages for a class. Consider the Wikipedia page for Dog: http://en.wikipedia.org/wiki/Dog The Dog page is in the category for Dogs. Why do we have a page for Dog and a category for Dogs? Because we need a page to talk about what the Dog class is, and we need a category so that other pages about particular dogs can belong to it. But the relation between the page Dog and the category Dogs is not instance/class. Instead, SMW should support a new relation for this. The Dog page is also in the category Cosmopolitan Species, which is actually correct for an instance/class relation. But notice that Dog is already a class, so Cosmopolitan Species is a "class of classes" - a second order class. Another example of a "class of classes" is Heads of State. For example, President and Emporor are instances of the class Heads of State. But President itself is *already" a class, which can have instances like George Washington. So there is not a clean boundary where a page is always an individual instance and a category is always (first order) class. This really confuses most people and I think the SMW developers gave up on the idea that people could keep it straight, so it has been left in its vague messy state. I'm not happy with it, but to fix it requires a will to force the SMW user to understand second order classes. - Jeff ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Semediawiki-devel mailing list Semediawiki-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/semediawiki-devel
