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RE: lcsh.info RDFa SKOS and content negotiation - use of RDF-style # IDs in RDFa?

From: Williams, Stuart (HP Labs, Bristol) <skw@hp.com>
Date: Tue, 30 Sep 2008 16:16:34 +0000
To: Steven Pemberton <steven.pemberton@cwi.nl>, Dan Brickley <danbri@danbri.org>, RDFa <public-rdf-in-xhtml-tf@w3.org>, "www-tag@w3.org WG" <www-tag@w3.org>
CC: Ed Summers <ehs@pobox.com>
Message-ID: <233101CD2D78D64E8C6691E90030E5C81B6CF1A95E@GVW1120EXC.americas.hpqcorp.net>

Hello Steven,

> -----Original Message-----
> From: Steven Pemberton [mailto:steven.pemberton@cwi.nl]
> Sent: 30 September 2008 13:55
> To: Williams, Stuart (HP Labs, Bristol); Dan Brickley; RDFa;
> www-tag@w3.org WG
> Cc: Ed Summers
> Subject: Re: lcsh.info RDFa SKOS and content negotiation -
> use of RDF-style # IDs in RDFa?
>
> On Tue, 30 Sep 2008 14:35:52 +0200, Williams, Stuart (HP
> Labs, Bristol)
> <skw@hp.com> wrote:
> >> My preferred practice for naming concepts is to use blank
> >> nodes and then
> >> foaf:primaryTopicOf to ground them:
> >>
> >>         <link about="_:StevenPemberton" rel="foaf:primaryTopicOf"
> >> href="http://www.cwi.nl/~steven/" />
> >>         <link about="_:Amsterdam" rel="foaf:primaryTopicOf"
> >> href="http://www.amsterdam.nl/" />
> >>         <link about="_:W3C" rel="foaf:primaryTopicOf"
> >> href="http://www.w3.org/" />
> >>         <link about="_:TheWasteLand" rel="foaf:primaryTopicOf"
> >> href="http://en.wikipedia.org/wiki/The_Waste_Land" />
> >>         <link about="_:Love" rel="foaf:primaryTopicOf"
> >> href="http://en.wikipedia.org/wiki/Love" />
> >>
> >> <span about="_:TheWasteLand" property="dc:creator">T.S.
> Eliot</span>
> >> <a about"_:W3C" rel="foaf:homepage"
> href="http://www.w3.org/">W3C</a>
>
> (Editorial fix s/primaryTopicOf/isPrimaryTopicOf/G)

Now you have, eg:

_:StevenPemberton foaf:isPrimaryTopicOf <http://www.cwi.nl/~steven/> .

> > How does that work for merging information from different
> sources about
> > the same given primary topic?
>
> I'm not sure what the problem is, but does this answer your question?
>
> "The foaf:isPrimaryTopicOf property is inverse functional: for any
> document that is the value of this property, there is at most one thing in
> the world that is the primary topic of that document. This is useful, as
> it allows for data merging, as described in the documentation for its
> inverse, foaf:primaryTopic.: http://xmlns.com/foaf/spec/#term_isPrimaryTopicOf

Only parially. *iff* the primary topic node were not blank, but a definite URI node, then merging would world provided that equivalent nodes were involved.

However, the identity of blank nodes is scoped only to the graph that they are in. If you have the two graphs:

{
_:StevenPemberton foaf:isPrimaryTopicOf <http://www.cwi.nl/~steven/> .
}

{
_:StevenPemberton foaf:isPrimaryTopicOf <http://www.w3.org/People/all#steven> .
}

You cannot determine that they both named resources have the same primary topic - so the blank topic node in this case is basically useless establishing that what we have are different accounts of Steven Pemberton.

IIUC isPrimaryTopicOf is intended to establish the use of say http://www.cwi.nl/~steven/ as a subject indicator for Steven Pemberton. As a subject indicator the resource can only be a subject indicator for one thing (hence inverse functional) - though there may be many subject indicators for a given thing. So if we have the merged graph:

{
        ex1:StevenPemberton foaf:isPrimaryTopicOf <http://www.cwi.nl/~steven/>, <http://www.w3.org/People/all#steven> .
        ex2:StevenPemberton foaf:isPrimaryTopicOf <http://www.w3.org/People/all#steven> .
}

We can deduce that ex2:StevenPemberton is owl:sameIndividualAs ex1:StevenPemberton (might be owl:sameAs) from the inverse functional nature of isPrimaryTopicOf.


> Best wishes,
>
> Steven

Stuart
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Received on Tuesday, 30 September 2008 16:19:34 GMT

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