- From: David Booth <david@dbooth.org>
- Date: Mon, 13 Jun 2011 16:50:48 -0400
- To: Jonathan Rees <jar@creativecommons.org>
- Cc: Jeni Tennison <jeni@jenitennison.com>, "www-tag@w3.org List" <www-tag@w3.org>
On Mon, 2011-06-13 at 13:51 -0400, Jonathan Rees wrote: > On Mon, Jun 13, 2011 at 11:30 AM, Jeni Tennison <jeni@jenitennison.com> wrote: > > Hi, > > > > For those who don't follow it, there's a thread on httpRange-14 / Issue-57 at the moment on the linked data mailing list. A good example message is: > > > > http://lists.w3.org/Archives/Public/public-lod/2011Jun/0186.html > > > > where Richard says: > > > > Being useful trumps making semantic sense. The web succeeded *because* > > it conflates name and address. The web of data will succeed *because* > > it conflates a thing and a web page about the thing. > > > > <http://richard.cyganiak.de/> > > a foaf:Document; > > dc:title "Richard Cyganiak's homepage"; > > a foaf:Person; > > foaf:name "Richard Cyganiak"; > > owl:sameAs <http://twitter.com/cygri>; > > . > > > > I don't think that this is covered by any of the scenarios in Jonathan's document at: > > My *intent* was that this situation would be covered by > 4.4 Coerce an information resource to what it defines its URI to name > but I guess the section name and description are not adequately evocative. > > I actually don't object to this attitude too much; if people want to > opt out of machine inference who am I to say otherwise. They > themselves say they don't care about it (i.e. inference is best done > in some subtle and complicated way by people, not in a simple and > stupid way by computers). Should they decide to care in the future, > they can generate new RDF. It might be a lost opportunity and an > interoperability risk, but so it goes - the horse has been led to > water and it finds the water unpalatable. I do not think that is a fair characterization. Richard's example is *not* opting out of machine inference. It is merely opting out of certain inferences that *some* applications need but others do *not* need. And that is as it *should* be, as it is not possible to cater to *all* applications. The subtle mistake that is being made repeatedly here is in assuming that someone's data is *wrong* (or socially irresponsible) if it conflates two things that we humans find useful to distinguish, such as people versus web pages -- *even* if the class of applications for which that data is intended have no need to make such a distinction! This is myth #4 in "Resource Identity and Semantic Extensions: Making Sense of Ambiguity": http://dbooth.org/2010/ambiguity/paper.html#myth4 > > > http://www.w3.org/2001/tag/awwsw/issue57/20110531/ > > > > In particular, I don't think the kind of 'punning' that we talked > about (where different properties treat the given resource as being > different kinds of thing) copes with the rdf:type property (shortened > to 'a' in the Turtle) having two different values. > > Correct. I think that in addition to expanding all the properties, > you'd also have to expand all the types, so that 'information resource > defining its URI to be a person' is a subclass of Person and so on. I > can add this to the presentation. > > > Similarly, it's really unclear in the above example whether the > > owl:sameAs relates to the Person or the Document (until you find a > > description of <http://twitter.com/cygri>, which of course might be > > a resource that is both a Document and a Person itself). > > I think it has to be the Document, at the level of sameAs, since > otherwise you get false equations between documents that describe the > same thing. No, you only get false equations if you *also* try to assert that foaf:Document is disjoint with foaf:Person. *Your* applications may need to make that distinction, but that is an issue with the *combination* of your application and Richard's data. It is not an issue with Richard's data per se: his data is perfectly fine for other applications that have no need for that distinction. > That assumes an entailment regime that can lead you to > such conclusions... RDFS entailment can't, so as long as you stay away > from interoperation with OWL content, sameAs doesn't mean anything in > particular, and there's no risk of inconsistency. > > This community ought to be perfectly happy with me saying the URI > refers to the information resource, since otherwise they'd be > admitting that the assignment *does* matter! > > The thing to do is to get this community involved in specifying how to > write metadata, e.g. embedded license declarations for RDF files that > are about information resources, The licensing example is a *very* good one, as it aptly demonstrates the problem that this ambiguity creates for *that* class of applications. But I think it would be a mistake to suggest that *all* socially responsible data should support that class of applications. -- David Booth, Ph.D. http://dbooth.org/ Opinions expressed herein are those of the author and do not necessarily reflect those of his employer.
Received on Tuesday, 14 June 2011 00:39:00 UTC