Clarifying:
The function of an ID (identifier) is to identity a concept, not to
describe it. So they must be unique by definition, a concept can not have
multiple IDs . Multiple concepts may be equivalent to one another, but
that doesn't mean they are the same. If you have two different IDs (i.e.
the Unicode comparison of the strings results in mismatch) you have by
definition two different concepts. That is not what you want. You want
multiple labels for the same concept/ID.
The description of a concept (or definition, philosophically speaking) is
the whole group of other properties you ascribe to the concept by
referencing its ID, including as may human readable labels as you need and
relations to other concepts. You can choose to use an automatic generated
ID in order to guarantee uniqueness or use manually ascribed human
readable strings, but with the later you must guarantee the uniqueness by
process (as is the case with DBpedia IDs, which are derived from Wikipedia
IDs).
It is not a RDF requirement for the IRIs to be simple (although that saves
parsing time) or human readable, but they MUST be unique and stable,
otherwise the identity of the concept is compromised. Human readable IDs
are only helpful in manual edition of files, which happens only in
examples and didactic purposes. Real world IDs are mostly UUIDs
(universally unique IDs) generated by the system (for Java, see
java.util.UUID ). Some systems use prefixed URLs in order to embed
provenance into the ID, but that is a very, very bad practice: provenance
is metadata as any other, you should use specific properties for that. IDs
were not designed to provide any other semantics besides identity.
Cheers.
=============================================
Marcelo Jaccoud Amaral
PETROBRAS
Tecnologia da Informação e Comunicações - Arquitetura Tecnológica
(TIC/ARQTIC/AT)
=============================================
dum loquimur, fugetir invida aetas: carpe diem, quam minimum credula
postero.
-- Horatius
De: Katie Frey <kf...@cfa.harvard.edu>
Para: Markus Kroetzsch <markus.kroetz...@tu-dresden.de>
Cc: "DBpedia Discussion \(ML\)"
<dbpedia-discussion@lists.sourceforge.net>
Data: 2016-05-31 11:50
Assunto: Re: [Dbpedia-discussion] Concept Identifiers
Dear Markus,
Thank you for the insight. We might also try to assign both numeric and
descriptive IDs to a concept. It seems as though best practices don't
really exist in this area, other than the general imperative to keep the
URIs simple and as stable as possible.
Best,
Katie
--
Katie E. Frey
John G. Wolbach Library, Harvard-Smithsonian Center for Astrophysics
60 Garden Street, MS-56, Cambridge, MA 02138
email: kf...@cfa.harvard.edu | phone: 617-496-7579
http://astrothesaurus.org | http://library.cfa.harvard.edu/
"Surprising what you can dig out of books if you read long enough, isn’t
it?"
- Rand al'Thor (in Robert Jordan's The Shadow Rising, Book Four of the
Wheel of Time)
"This is insanity!" "No, this is scholarship!"
- Yalb and Shallan (in Brandon Sanderson's Words of Radiance, Book Two of
the Stormlight Archive)
On Thu, May 26, 2016 at 4:06 PM, Markus Kroetzsch <
markus.kroetz...@tu-dresden.de> wrote:
Dear Katie,
DBpedia mostly uses descriptive URIs that are based on the titles of
Wikipedia articles in a specific language. These URIs change if pages are
renamed, but for many concepts, this does not occur so often. You would
probably only notice it if you are using the URIs for several years.
If you instead want to use numeric IDs based on Wikipedia pages (or
DBpedia URIs), you can take them from Wikidata. These IDs are stable, but
not descriptive. They are kept unique in that they can only be deleted but
not reused. For example, http://dbpedia.org/page/Solar_System is currently
the same as
https://www.wikidata.org/entity/Q544.
The Wikidata URI uses content negotiation to redirect you to the HTML page
if you open it in a browser, and to RDF if you open it with an RDF
crawler. See https://www.wikidata.org/wiki/Wikidata:Data_access for direct
links to the RDF content.
To manually find out what the Wikidata ID is for a Wikipedia page, you can
go to the Wikipedia page and use the link to "Wikidata item" on the left.
To do this in an automated fashion, you can use the SPARQL endpoint, e.g.,
with the query
SELECT *
WHERE {
<https://en.wikipedia.org/wiki/Solar%20System> schema:about ?item .
}
(try it in the Wikidata SPARQL UI: http://tinyurl.com/jlk4fz2)
The Wikidata Web API can also map page titles to IDs for you prefer JSON
over SPARQL:
https://www.wikidata.org/w/api.php?action=wbgetentities&format=json&sites=enwiki&titles=Solar+System&props=
Each of these methods can also be used to fetch many IDs at once. So
basically it is fairly straightforward to translate from DBpedia URIs to
Wikidata URIs. The mapping between the two changes over time only when
DBPedia URIs change their meaning (e.g., if "Solar System" is renamed to
"Solar System (astronomy)" or something).
Best regards,
Markus
On 26.05.2016 20:43, Katie Frey wrote:
Hello,
How are concept IDs handled for DBpedia? It looks like the concept URIs
are descriptive (i.e. for the concept
http://dbpedia.org/page/Solar_System, the concept ID is
"Solar_System"). Are the descriptive IDs used throughout all of dbpedia
(back and front end) or are terms ultimately kept unique by using
numeric identifiers?
I've been developing a controlled vocabulary and I would also like to
use URIs so that my terms can be used with other linked data schemes.
My group and I have had a lot of discussions regarding the concept IDs;
some want them to be descriptive, based on the preferred term for each
concept so that they are human readable but this could cause problems if
the terms used to describe each concept change over time, others want
them to be randomly generated so that if the description of a term
drifts over time the URI for the concept will always remain static.
We are trying to figure out if there are any standards or best practices
we should be looking towards when it comes to concept IDs. Any
thoughts/comments/justifications would be appreciated.
Best,
Katie
--
Katie E. Frey
John G. Wolbach Library, Harvard-Smithsonian Center for Astrophysics
60 Garden Street, MS-56, Cambridge, MA 02138
email: kf...@cfa.harvard.edu <mailto:kf...@cfa.harvard.edu> | phone:
617-496-7579 <tel:617-496-7579>
http://astrothesaurus.org | http://library.cfa.harvard.edu/
"Surprising what you can dig out of books if you read long enough, isn’t
it?"
- Rand al'Thor (in Robert Jordan's The Shadow Rising, Book Four of the
Wheel of Time)
"This is insanity!" "No, this is scholarship!"
- Yalb and Shallan (in Brandon Sanderson's Words of Radiance, Book Two
of the Stormlight Archive)
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