Re: Person Identifier

hi Bent,

[posting back to the list]

> Well, I'm not really confused about speaking about a web page or  
> speaking about a person, because a type designation should reveal  
> that.
> <my-uri/iri> rdf:type ont:Person
> <my-uri/iri> rdf:type ont:WebPage

yes. But what if you only have the URI in the first place without any  
rdf:type property? You do a HTTP GET and look for <my-uri/iri>  
rdf:type ?t. If there is no connection, and Ian is right of course,  
you have no information about the type. To make an application  
workable offline, you just have to make sure type information is  
alrady there locally.

> I was just a little annoyed at the dependency on HTTP and  
> questioning the best way to identify people using URIs.
>
> "urn:person:" + sha1(ssn)?
>
> Using HTTP sort of implies you can dereference it and that may not  
> always be true. Defererencing it can even be misleading.
>
> Imagine
>
> 2000: Joe Black: http://joeblack.com/foaf.rdf
> 2020: Joe Smith Black: http://joeblack.com/foaf.rdf

I've read again your original post and I'm afraid this is much more an  
issue than HTTP/non-HTTP URIs. I'm sure there have been many  
discussions about that here on the list.

As you said: "Of course one can also apply a weaker "extensional"  
meaning of identity and compare for equality on a property level." - I  
think this is currently the common sense, isn't it?

Encoding date/timestamps into URIs may solve troubles with different  
versions and you can add version properties into your newer documents  
(see [1]) to tight them together.

But it brings in other issues like different URIs for evolving  
vocabs.... Read this: "The FOAF vocabulary is identified by the  
namespace URI 'http://xmlns.com/foaf/0.1/'. Revisions and extensions  
of FOAF are conducted through edits to this document, which by  
convention is accessible in the Web via the namespace URI. For  
practical and deployment reasons, note that we do not update the  
namespace URI as the vocabulary matures."  [2]

Regards,
Andy

[1] http://www.w3.org/TR/owl-ref/#VersionInformation
[2] http://xmlns.com/foaf/spec/

----------------------------------------------------------------------
Dipl.-Ing.(FH) Andreas Langegger
Institute for Applied Knowledge Processing
Johannes Kepler University Linz
A-4040 Linz, Altenberger Straße 69
http://www.langegger.at