On 27 Oct 2009, at 09:57, Bernhard Eversberg wrote:
> Alexander Johannesen wrote:
>> Seems some of my stuff on identity management has gone unanswered, so
>> I've written a quick blog post to try to clarify why this is
>> important, why this is how you should at least ponder identity in an
>> RDF world, and on cataloging using nothing but URIs for both subject
>> and resource identity ;
> URIs are bad identifiers, for one reason: URIs always contain
> verbal components, and words (names are words too) - sooner or later
> - get changed. Also, the syntax of an URI might be valid for less than
> eternity.
> Least prone to changes are plain numbers.
> Example:
> Currently, one might be tempted to use WorldCat Identities for URIs.
> Here is one:
>
> http://orlabs.oclc.org/Identities/lccn-n79-3362
Whatever identifier scheme you use is prone to change - we all know
how unique ISBNs are for instance!
Many elements in that OCLC URI you quote could well change. The
Linked Data approach to this issue is to spread information widely
across more than one authority. By identifying other sources of the
same data has two major benefits.
Firstly, it introduces a powerful network effect. If a source of data
references a concept, that your data also references, you can you can
draw some conclusions about the connection between that data source
and your own. So if two data sets, which do not reference each other,
both reference a subject (a country for example) page in DBpeadia you
can use that shared concept to produce an aggregated view of those two
sets. Thus adding value to both sets.
Secondly, it builds in automatic redundancy. If one of the
authorities for a particular concept changes, or even disappears, the
URI is still a valid identifier which can (via sameas assertions)
still be used to identify resources hosted by another authority.
For example take a look at this record at semanticlibrary.org
(remember this is an experimental site at the moment): http://semanticlibrary.org/items/5059.html
and its RDF representation:
http://semanticlibrary.org/items/5059.rdf (dependant on your browser
you may need to view source to see the RDFXML representation)
About halfway down you will see:
<owl:sameAs rdf:resource="http://www4.wiwiss.fu-berlin.de/bookmashup/books/0439786770
"/>
<owl:sameAs rdf:resource="http://semanticlibrary.org/isbn/9780439786775
"/>
<owl:sameAs rdf:resource="http://semanticlibrary.org/isbn/0439786770
"/>
<owl:sameAs rdf:resource="http://semanticlibrary.org/lccn/2005921149
"/>
Where references to the same concept at other URIs are linked to the
concept we are viewing. Some inside the same data store, others out
across the linked data web.
When loading data into a Linked Data store, identifying URIs to other
descriptions of the same thing, is a comon way of operating. By
having an easily understandable URI structure helps make this easy to
do automatically for well know identifiers.
~Richard.
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Received on Tue Oct 27 2009 - 06:52:30 EDT