RE: Property instantiation

Hi Frank,

Thanks for your response!
Please see my reactions below.

Regards,
Hans

PS I attach a png file with my perception of how RDF-RDFS-OWL fits together.
Please shoot at it, if incorrect.

-----Original Message-----
From: semantic-web-request@w3.org [HYPERLINK
"mailto:semantic-web-request@w3.org"mailto:semantic-web-request@w3.org] On
Behalf Of Frank Manola
Sent: Monday, April 17, 2006 17:37
To: Hans Teijgeler
Cc: SW-forum
Subject: Re: Property instantiation


Hans--

I'm not going to try to tackle the example you sent offlist until I
understand the simpler one!

As far as I can tell, the simple answer to "is
creator        rdf:type      isAuthorOf?"
is "no".  That isn't necessarily same as the answers to the other questions
(I don't see them as being "i.e.", at least not yet).
[HT] No is a clear answer.

I say "as far as I can tell" because I have some questions.

1.  Specifically, what do you mean by "triple at the OWL level"?  In the
triple "Specialist  isAuthorOf   W3CRecommendation", I assume that
Specialist and W3CRecommendation are classes, but how is isAuthorOf defined?
As an owl:ObjectProperty?  As a *subproperty* of owl:ObjectProperty?  Note
also that OWL can have "instances" (but I'm assuming that when you say "OWL
level" you really mean at the level where you define classes, right?).

[HT] As an instance of owl:ObjectProperty, assuming that Specialist and
W3CRecommendation are instances of owl:Class.

2.  when you say you have "an instance such as
frank          creator        rdfPrimer",

a.  do you mean that this is supposed to be an instance of a "metalevel"
triple "Specialist  isAuthorOf   W3CRecommendation"?  But there's no
explicit connection between them given (that's mainly why my simple answer
was no).  How are frank, creator, and rdfPrimer defined?

[HT] frank rdf:type  Specialist ,  and   rdfPrimer  rdf:type
W3CRecommendation . I asked whether in that case creator  rdf:type
isAuthorOf, but I guess the answer is still 'no'.

3.  Regarding "instantiating properties", an instance of a property is a
subject/object pair (OWL Reference, Section 4).  Could you clarify what you
mean?

[HT] If I have the triple Specialist --- isAuthorOf --- W3CRecommendation as
explained above,  and given the typing frank --- rdf:type --- Specialist,
and rdfPrimer --- rdf:type --- W3CRecommendation then I think that if I
cannot state that creator --- rdf:type --- isAuthorOf  I have an
uncertainty, because there may be more than one such subject/object pair.
Or is the answer to this problem that the name of the property at owl class
level and at instance level shall be the same?

4.  By "metaclasses of "Property" do you by any chance mean *subclasses* of
Property (in OWL, either ObjectProperty or DatatypeProperty)?  E.g., instead
of defining isAuthorOf as having rdf:type owl:ObjectProperty (i.e., as being
an instance of a property), do you intend to define isAuthorOf as being a
*subclass* of owl:ObjectProperty?  (You can do that, but wouldn't, say,
defining creator as a subpropety of isAuthorOf do what you want?)

[HT] I was not intending to define subclasses of ObjectProperty, so I start
to believe that the answer to my previous question (having the same property
name at class and instance level) will be 'yes'. .

If I'm missing things that are really obvious, my excuse is I have a cold.
Also it's a holiday here (Patriot's Day--the start of the Revolutionary
War), so further responses may be kind of slow.

[HT] I am grateful that you responded at all, given those circumstances! I
wish you "beterschap!" (get well, in Dutch)

--Frank


Hans Teijgeler wrote:
> Frank,
> 
> Small question, simple answer:
> If I have a triple at OWL level, such as

Specialist  isAuthorOf   W3CRecommendation

> and an instance such as

frank          creator        rdfPrimer

> then is

creator        rdf:type      isAuthorOf  ?

> i.e. do you also instantiate Properties?
> i.e. can I also have metaclasses of Property?
> 
> Regards,
> Hans
>

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