Hi Fabian,
On 19/09/14 16:12, Fabian Cretton wrote:
Thank you Sergio, thinks become clearer, I start understanding why you
said that our overLOD functionality really looks like LDCache.
That's good, things start to become clearer.
But there is still a behavior I don't understand.
I did load "http://sws.geonames.org/2658434/about.rdf"; not being
interested in the file's URI
<http://sws.geonames.org/2658434/about.rdf>
and its description's triples, but being obviously interested in
<http://sws.geonames.org/2658434/>and ( http://sws.geonames.org/2658434/
) its triples.
As this .rdf file contains the two resources, I guess LDCache does try
to update both of them, and:
- for <http://sws.geonames.org/2658434/about.rdf> it is able to find
the file, download it, and extract only the part where
<http://sws.geonames.org/2658434/about.rdf> is a subject
- for <http://sws.geonames.org/2658434/>, LDCache, without further
configuration, is not able to handle the content negociation that
happens when opening this URL, and so there is no mention about any
update of <http://sws.geonames.org/2658434/> in the log files.
Is that correct ?
Not really. Geonames supports Linked Data:
$ curl -I http://sws.geonames.org/2658434/ -H "Accept: application/rdf+xml"
HTTP/1.1 303 See Other
Date: Fri, 19 Sep 2014 14:26:25 GMT
Server: Apache/2.2.17 (Linux/SUSE)
Location: http://sws.geonames.org/2658434/about.rdf
Content-Type: text/html; charset=iso-8859-1
So LDCache should update it too. We'd need to debug what's happening
there. Could you please verify there is no traces of such update in the
logs?
But then, there is something still strange to me:
I did also upload my personal foaf file:
http://www.websemantique.ch/people/rdf/fabiancretton.rdf
This file don't contain any information about the resource
<http://www.websemantique.ch/people/rdf/fabiancretton.rdf (
http://www.websemantique.ch/people/rdf/fabcretton.rdf )>, but only about
myself: <http://www.websemantique.ch/people/fabiancretton>
Nevertheless, LDCache does have the same behavior as for the geonames
resource:
09:09:27.023 INFO o.a.m.l.s.p.AbstractHttpProvider - retrieving
resource data for
http://www.websemantique.ch/people/rdf/fabiancretton.rdf from 'Linked
Data' endpoint, request URI is
<http://www.websemantique.ch/people/rdf/fabiancretton.rdf>
09:09:27.352 INFO o.a.m.l.s.p.AbstractHttpProvider - retrieved 0
triples for resource
http://www.websemantique.ch/people/rdf/fabiancretton.rdf; expiry date:
Fri Sep 19 09:09:27 CEST 2014
So where did LDCache find
<http://www.websemantique.ch/people/rdf/fabiancretton.rdf> ?
I might be wrong, and the imported URI could be registered somewhere
else for later updates. Probably Jakob would know it.
BTW, your personal URI is not retrievable according the Linked
Principles and the httpRange-14 resolution, because it returns 300
instead of the normative 303.
I did name the context
<http://www.websemantique.ch/people/rdf/fabiancretton.rdf> -> does
LDCache also take into account the contexts names ?
No, LDCache is not aware of contexts (named graphs).
Another critical aspect about LDCache I'd like (as others I guess) to
understand:
How does LDCache handle the 'update' of those information ? How does it
know that a triple did came from a web resource (and should be updated),
and how does it know that a triple was added afterwards (and should be
kept for instance) ?
Let say I have a bunch of triples with
<http://www.websemantique.ch/people/fabiancretton> as a subject. Those
triples are loaded from the web. LDCache will do some updates, thus
deleting all triples where
<http://www.websemantique.ch/people/fabiancretton> is subject, and the
reimporting all triples where
<http://www.websemantique.ch/people/fabiancretton> is subject, is that
correct ?
in the mean while, I did add a new triple with
<http://www.websemantique.ch/people/fabiancretton> as a subject -> will
it be deleted by LD Cache ?
Not sure. That's an inherited problem of the RDF data model and the Open
World assumption. But actually that's a good point; I'll also discuss it
with Jakob on Monday.
Thanks for your feedback.
Cheers,
--
Sergio Fernández
Senior Researcher
Knowledge and Media Technologies
Salzburg Research Forschungsgesellschaft mbH
Jakob-Haringer-Straße 5/3 | 5020 Salzburg, Austria
T: +43 662 2288 318 | M: +43 660 2747 925
sergio.fernan...@salzburgresearch.at
http://www.salzburgresearch.at
