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Re: Skolemization and RDF Semantics

From: Dan Brickley <danbri@danbri.org>
Date: Thu, 21 Apr 2011 12:10:40 +0200
Message-ID: <BANLkTimzjoQ0N41LjsFBnPxuE1-bsq19=Q@mail.gmail.com>
To: Pat Hayes <phayes@ihmc.us>
Cc: Richard Cyganiak <richard@cyganiak.de>, Steve Harris <steve.harris@garlik.com>, David Wood <dpw@talis.com>, "RDF-WG public-rdf-wg@w3.org" <public-rdf-wg@w3.org>, Margaret Warren <info@margaretwarren.us>
On 21 April 2011 00:07, Pat Hayes <phayes@ihmc.us> wrote:
>
> On Apr 20, 2011, at 7:10 AM, Richard Cyganiak wrote:
>
>> Hi Pat,
>>
>> On 17 Apr 2011, at 15:15, Pat Hayes wrote:
>>>> First of all, it is *sometimes* but not *always* bad to use blank nodes. The documents I linked to gave specific advice, informed by implementation experience, for when to use, and when to avoid, blank nodes.
>>>
>>> True, but it does say that the fewer bnodes the better, as a general rule about all data.
>>
>> Well, you gotta simplify when talking to the man on the street. A more accurate phrasing: Substituting a blank node with a URI never makes data less useful. (Assuming the blank node is actually used as a local name and not an existential variable, which is the case for all data published on the Web that I've ever seen, with the exception of blank nodes in rdf:Lists.)
>
> I dont think you need to add the qualification, actually. Just say, it never makes it less useful *when you can do it*..

It can make it less useful as a record of who-said-specifically-what.

If the original graph, sourced to -say- Steve, was

<Person><name>Dan Brickley</name><homepage
rdf:resource="http://hitdanback.com/"/></Person>

(I assume you all have built-in mental RDF/XML parsers by now...)

...and Pat rewrites it to be

<Person rdf:about="http://genid.pathayes.example.net/12349876"><name>Dan
Brickley</name><homepage
rdf:resource="http://hitdanback.com/"/></Person>

...then republishes it, still attributed to Steve, the data is
somewhat less useful. Because Steve didn't even mention that URI,
which casts doubt on Pat's reliability when relaying what triples
other's have asserted.

cheers,

Dan
Received on Thursday, 21 April 2011 10:11:08 GMT

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