W3C home > Mailing lists > Public > w3c-rdfcore-wg@w3.org > January 2003

Re: Schema LCC review

From: Brian McBride <bwm@hplb.hpl.hp.com>
Date: Wed, 15 Jan 2003 11:16:37 +0000
Message-Id: <5.1.0.14.0.20030115105028.032bbbb8@localhost>
To: Jan Grant <Jan.Grant@bristol.ac.uk>, RDFCore Working Group <w3c-rdfcore-wg@w3.org>

Jan,

In the light of your comments, I propose the following changes to the last 
call candidate:

strike:

[[As such, RDF data can resemble an entity-relationship diagram.]]

strike:

[[
Note that if a class were the same thing as the set of its instances
then common (Zermelo-Fraenkel) set theory would prevent it being an
instance of itself.]]

replace:
   http://www.w3.org/2001/sw/RDFCore/TR/WD-rdf-schema-20030117/#ch_range

[[states that P is an instance of the class rdf:Property, that C is an
instance of the class rdfs:Class and that the objects of triples whose
predicate is P are instances of the class C.]]

with

[[states that P is an instance of the class rdf:Property, that C is an
instance of the class rdfs:Class and that the resources denoted by objects 
of triples whose predicate is P are instances of the class C.]]

replace
   http://www.w3.org/2001/sw/RDFCore/TR/WD-rdf-schema-20030117/#ch_domain

[[states that P is an instance of the class rdf:Property, that C is a 
instance of the class rdfs:Class and that the subjects of triples whose 
predicate is P are instances of the class C.]]

with

[[states that P is an instance of the class rdf:Property, that C is a 
instance of the class rdfs:Class and that the resources denoted by subjects 
of triples whose predicate is P are instances of the class C.]]

replace
   http://www.w3.org/2001/sw/RDFCore/TR/WD-rdf-schema-20030117/#ch_subclassof

[[...is used to state that one class is a specialization of another.]]

with

[[ ... is used to state that all the instances of one class are instances 
of another.]]

replace
   http://www.w3.org/2001/sw/RDFCore/TR/WD-rdf-schema-20030117/#ch_subpropertyof

[[The property rdfs:subPropertyOf is an instance of rdf:Property that is 
used to specify that one property is a specialization of another.]]

with

[[The property rdfs:subPropertyOf is an instance of rdf:Property that is 
used to specify that all resources related by one property are also related 
by another.]]

Brian





At 12:03 14/01/2003 +0000, Jan Grant wrote:

>Typos, trivial stuff, one issue (which is raised here because you've
>carefully not said much about seeAlso &co., so not necessarily a schema
>problem)
>
>
>1. Introduction
>
>"As such, RDF data can resemble an entity-relationship diagram."
>
>An instance diagram, maybe, but I think this sentence is empty and can
>be struck. The traditional distinction between class and instance is
>blurred by RDF.

I tend to agree about striking that sentence.



>2. Classes
>
>"Note that if a class were the same thing as the set of its instances
>then common (Zermelo-Fraenkel) set theory would prevent it being an
>instance of itself."
>
>This comes across more clearly in the MT; strike this sentence on the
>grounds of being woolly.

Again, I'm tempted to agree and would suggest it goes now.



>"A class C is a subclass of a class C' if and only if all the instances
>of C are also instances of C'."
>
>Again, this is what the MT says, but I still find it incongruous that
>classes have an intensional semantics yet the primary relationship
>between them is extensional. I'd prefer a purely intensional definition:
>
>"If a class C is a subclass of a class C', then all instances of C are
>also instances of C'." See below.

That is not what we have decided.



>2.1 rdfs:Resource
>
>Formatting error. (no heading style?)

Fixed



>3.1 rdfs:range
>
>"The triple
>
>         P rdfs:range C
>
>states that P is an instance of the class rdf:Property, that C is an
>instance of the class rdfs:Class and that the objects of triples whose
>predicate is P are instances of the class C."

There is a use/mention error there.  That should be "the objects of 
statements ..." since the object of a triple is a URI.  I propose fix 
before last call.


>All those things are true as a consequence of the semantics document
>(since rdfs:range rdfs:domain rdfs:Property is an RDFS axiomatic triple)
>but does this triple _state_ all those conclusions or does it _entail_
>them? because it only RDFS-entails these conclusions, not rdf-entails
>them. Same comments (I think) apply to 3.2 and 3.3 (consider this
>preemptive nitpicking)

OK, I'll ignore it.



>3.2, 3.3 Heading formatting error.

fixed



>3.4 rdf:subClassOf
>
>"...is used to state that one class is a specialization of another."
>
>No it isn't; it's used to state a subset relationship between their
>class extensions. You've carefully pointed out the difference between
>two intensionally distinct classes with the same extension in section 2.
>Don't ignore it here. Using your example, consider the class of everyone
>living in the UK as collected bythe tax office. Can you honestly say
>that the post office's class of people at a particular "zip code" is a
>speciali[sz]ation of that?

Right. That should be fixed.



>5.2 RDF Collections
>
>SEMANTICS doesn't require that the collections structures are
>well-formed. Do you want to point that out here? What is your answer to
>the question, "are RDF Collections required to be well-formed?"

Not by RDFS, but I don't want to draw attention to it.



>5.4.1 rdfs:seeAlso
>
>You carefully don't say much here, which is good. However, I think this
>raises an issue which we should address (even if it's to punt) before or
>as part of LC:
>
>         If a resource is named by something that looks like a URI,
>         then what expectations can we have about that? If we (through
>         some process) dereference that URI, what can we expect to
>         see? Ie, is there any expectation (and if so, when) that
>         the use of a web address to name something means that we
>         can get a description of the named thing by dereferencing that
>         address? Or does the web address name the description
>         itself?

We are going nowhere near that.  Way outside our charter.

>Consider this a last-call comment (to speed things along, ie get to LC)
>but I think we're doing the semantic web a disservice by not addressing
>this question - even if "addressing" the question involves punting to
>TAG. One explicit approach would be to introduce an explicit set of
>properties along these lines:
>
>         <eg:something> <rdfx:URI> "eg:something-else"^^<xsd:uri> .
>
>Same comments apply to 5.4.2; although the wording is careful here too.
Received on Wednesday, 15 January 2003 06:15:20 EST

This archive was generated by hypermail pre-2.1.9 : Wednesday, 3 September 2003 09:55:21 EDT