Hi Ray,

You can associate information with an ISBN as a URN, because it can be the subject of a triple, unlike a literal.  It's always a unique "thing", as opposed to a literal which is just a sequence of characters.  The other responses while I've been writing the below do a great job of discussing this, so I won't repeat them :)

To demonstrate the differences:

* Most simple, least functional:

_:x a bf:Instance ;
  bf:isbn10 "0738609080" .

(There's a string and you can infer that it's an ISBN due to the predicate, but can't do anything useful with it)

* Current example, with very unclear semantics (http://bibframe.org/vocab/isbn10.html

_:x a bf:Instance ;
  bf:isbn10 <http://isbn.example.org/0738609080> .  

(where this resource is thus a bf:Identifier with no properties, and thus very strange)

* Revised example, using bf:Identifier

_:x a bf:Instance ;
  bf:isbn10 [ a bf:Identifier ; 
    bf:identifierValue "0738609080" ; 
    bf:identifierScheme "isbn10" ]

(where this resource can't be referenced outside of the local context, as a blank node)
This is hard to find instances of, as you need to do:

?x a bf:Instance . ?x bf:isbn10 ?y . ?y bf:identifierValue "..." . ?y bf:identifierScheme "isbn10" .
Compare to the queries below...

* Potential model, where the ISBN identifies something very similar but not exactly the Instance:

_:x a bf:Instance ;
  bf:similarTo <http://isbn.example.org/0738609080> .

?x a bf:Instance . ?x bf:similarTo <uri> .

* Rob's preferred model, if the ISBN actually identifies the Instance:

<http://isbn.example.org/0738609080> a bf:Instance .

No need to do SPARQL as you already have the identifier of the resource :)



On Thu, Jul 17, 2014 at 1:45 PM, Denenberg, Ray <[log in to unmask]> wrote:
What would be the benefit of representing an isbn as a urn if it doesn't resolve?


> -----Original Message-----
> From: Bibliographic Framework Transition Initiative Forum
> [mailto:[log in to unmask]] On Behalf Of Stuart Yeates
> Sent: Thursday, July 17, 2014 4:34 PM
> To: [log in to unmask]
> Subject: Re: [BIBFRAME] BibFrame and Linked Data: Identifiers
> On 07/17/2014 09:39 AM, Denenberg, Ray wrote:
> > I think the advice is:
> >
> > (1) don't use a URI to identify a bf:Identifier.  Treat it as a blank node.
> >
> > (2) Only a non-URI identifier (e.g. isbn) should be treated a
> > bf:Identifier.  (I.e. a URI  should not be treated as a bf:Identifer.
> > Thus the property bf:uri should be eliminated.)
> >
> > I think there is consensus on this, someone correct me if I’m wrong.
> In real systems, won't ISBNs be represented as URNs in the namespace
> URN:ISBN:... as defined by http://www.ietf.org/rfc/rfc3187.txt ?
> Are there really any identifiers that we care that aren't already mapped to
> URNs? If yes, isn't the solution to map them to URNs?
> cheers
> stuart

Rob Sanderson
Technology Collaboration Facilitator
Digital Library Systems and Services
Stanford, CA 94305