- From: by way of <graham@wideman-one.com>
- Date: Tue, 20 Aug 2002 08:37:30 -0400
- To: www-rdf-comments@w3.org
[freed from spam filter -rrs] Date: Tue, 20 Aug 2002 07:20:43 -0400 (EDT) Message-Id: <4.1.20020820031956.0187f9e0@sunstroke.sdsu.edu> To: Brian McBride <bwm@hplb.hpl.hp.com>, Frank Manola <fmanola@mitre.org> From: graham wideman <graham@wideman-one.com> Cc: www-rdf-comments@w3.org Brian: Heh heh heh, your writing is helpful in tone, though I'm not sure whether I'm getting clearer or muddier :-) 1. You are right that *part* of what's confusing is the phrase "(or some subclass of rdfs:Class)". Absent that phrase, I would believe that if a resource Description has a property rdf:type...Class then that resource is a Class, and otherwise it's not. (If we can't delete that phrase, then I have no idea how to distinguish a Class from a non-Class.) Or maybe the escape hatch is that it's possible to write: rdf:type...SomethingThatsNotAClass Is that legit? If it is (and I'm now thinking it is) then the earlier sentence in the primer: "The RDF Schema *type* system allows resources to be defined as *instances* of one or more *classes*." ... is kind of misleading, since apparently the type system (ie: the system using the keyword "type") can define resources to be of something other than classes as well. 2. >I could define the class >bwm:ClassesDefinedByBrianMcBride to be a subclass of rdfs:Class. I could >then say something like: > bwm:ClassesDefinedByBrianMcBride rdfs:subClassOf rdfs:Class . > bwm:AClass rdf:type bwm:ClassesDefinedByBrianMcBride . > >This implies > > bwm:AClass rdf:type rdfs:Class . > >Now none of this says anything about the class hierarchy of bwm:AClass. We >know nothing about its sub and super classes. Eh? Er, I mean, yes indeed, this gets to the heart of the matter! You've written that AClass is of *type* ClassesDefinedByBrianMcBride, which is a *subClassOf* Class. Now, unless I really suspend disbelief, to me this looks like you've said that AClass has ancestors ClassesDefinedByBrianMcBride and Class! You say it doesn't mean that, and certainly there are two different keywords involved which presumably have two different intents, but I sure as heck can't tease out what the different intents are! Well, anyway, I could continue in this vein, finding all the things that don't make sense (to me at least), but I suspect they mostly have as root cause the same misunderstanding. Indeed, my suggestion of a table was intended to get at that issue by having an enumeration of popular combinations of rdf:type and subClassOf values and what is the nature of resource that results. Maybe I should have written it: type subClassOf Resource nature --------------------------------------- --- --- Can't be a class Class --- Must be a class Class #OtherClass Must be a class ClassA --- Not sure ClassA ClassB Not sure Property ??? A property ... more combos?... Thanks, Graham --------------------------------------------------- Graham Wideman Resources for programmable diagramming at: http://www.diagramantics.com graham@wideman-one.com http://www.wideman-one.com
Received on Tuesday, 20 August 2002 08:37:37 UTC