Hi guys,
On 04/11/14 11:44, Fabian Cretton wrote:
Because in my understanding of the web of data, anyone can say anything
about anything, isn't that correct ?
Not really if you consider trust...
For instance, there could be a specific product sold by different
vendors, and each vendor, publishing a catalog in RDF, will provide a
price for that product. So, referring to that produc'ts URI, each vendor
will publish data with the product's URI as subject. That seems a very
simple and realistic case, isn't it ?
No, I would not say so.
Let's use a concrete product as example, a car, VW Golf.
If the manufactured publishes information about that car:
<http://www.volkswagen.com/cars/golf/gte> vso:weight "1520" .
Then if a retailer sells a model of that car, publishing the following data:
<http://www.asturwagen.es/offer1> a gr:Offering ;
gr:includes <http://www.volkswagen.com/cars/golf/gte> .
<http://www.volkswagen.com/cars/golf/gte> vso:weight "1525" .
You should never trust what the retailer says that the weight of the
Golf GTE is 1,525 kg. The dealer has no authority to say that.
URIs are global identifiers using the hierarchical DNS system. You
cannot mint URIs you do not control for saying information about things
you do not own.
Back to you your product example, the vendor
Then can you help me to better understand what "is/should" a Marmotta's
LDClient ?
On that page [1], it is said that "LDClient is a flexible and modular
Linked Data Client (RDFizer
( http://www.w3.org/wiki/ConverterToRdf) )"
There is already something not clear for me in that sentence: RDFizing
is, to me, the process of transforming non-rdf data to rdf.
But if I understand it well, LDClient is already able to import natif
RDF, for instance RDFa, Linked Data and also querying a SPARQL
end-point.
Is LDClient designed to deal only with data published from its own URL,
where all triples have that URL as subject ?
It does RDFizing. But it also discards the triples that do not talk
about the URI that was referenced.
if so, what happens when LDClient is used as a RDFizer on non-RDF data
?
Maybe I should have a look at the RDFa client and also see how data is
processed there.
In the RDFa Data Provider is just a transformation process. The cases
that might be causing issues for understanding it could be other that
make use of APIs to get data out of other formats (e.g., the
transformation from Facebook Graph).
But here is what interest us in LDClient:
- import RDF and non-RDF data in the triple store (even if it is an RDF
file where subject don't correspond to the file's URL)
- import first in a temporary location, in order to import only part of
the data, and validate the data. It seems that LDClient does handle this
natively and this feature is very interesting for us.
OK, so let's put it this way: the general purpose of LDClient is to
respect the URI as identity for the data; but if you have a custom
scenario were that needs to be extended, you are completely free to use
the infrastructure provided by LDClient.
About dealing with data update, I understand that in your use of
LDCache/LDClient, ensuring that triples with a specific subject come
from one data source is a way to know which triples to update when
refreshing the data. In our case, we deal with 'contexts' (named graph)
to deal with that.
That's the business of LDCache, which uses a fixed context for caching
the data.
Talking about this, I do have another question: is it a problem for
Marmotta/Kiwi do deal with a certain quantity of contexts ? I know it is
not a problem with other triple stores as OWLIM for instance.
Yes, there is not limit on the context KiWi is able to manage.
BTW, if you are interested of keeping OWLIM it should be easy to provide
a backend for Marmotta...
Cheers,
--
Sergio Fernández
Partner Technology Manager
Redlink GmbH
m: +43 660 2747 925
e: [email protected]
w: http://redlink.co
