Jeff Thompson wrote: > Another example > of a "class of classes" is Heads of State. For example, President and > Emperor are > instances of the class Heads of State. But President itself is *already" a > class, which > can have instances like George Washington.
Sorry, I screwed up this example. (I'm even getting confused.) Head of State is *not* a second-order class containing President. It is the superclass of President. Here's the test: George Washington is a President, and George Washington is a Head of State. However, Official Title is a second order class containing instances like President and Emperor. Here's the test: President is an Official Title, but George Washington is *not* an Official Title. So SMW should support separate properties for "is a" and "subclass of" (apart from Category) because we have to handle: * a page like George Washington is a President, but the President category does not explain what a president is. That is on the President *page*, so you want to like there with "is a". * The President page can link to the Heads of State page through a "subclass of" relation. * The President page can also link to the Titles page through an "is a" relation. * Hence, a page can be an individual, a first-order class or a second-order class (like Title), etc. and the category system is not able to deal with this. * The only good argument for using Category for classes is that SMW already supports transitive lookup from a category to a super category. But that is laziness. We should be able to support that "subclass of" is also transitive. - 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
