hypermedia-driven Web query solving
Ruben Verborgh <[email protected]> Tue, 11 Mar 2014 16:56:22 +0000
| Newsgroups | gmane.comp.web.services.rest |
|---|---|
| Message-ID | <[email protected]> |
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Hi hypermedia/REST people,
You might like our latest hypermedia client implementation.
It solves queries over Linked Data by using hypermedia:
http://client.linkeddatafragments.org/
(Web version of https://github.com/LinkedDataFragments/Client).
A server offers basic Linked Data Fragments (http://linkeddatafragments.org=
/);
they are pieces of a dataset, together with metadata and controls.
The collection of fragments forms a hypermedia API.
The client is given a SPARQL query and one fragment of the dataset.
For instance, we start from the fragment
http://data.linkeddatafragments.org/dbpedia?object=3Ddbpedia%3ABarack_Obama
and the query:
SELECT ?p, ?c WHERE {
?p a <http://dbpedia.org/ontology/Artist>.
?p <http://dbpedia.org/ontology/birthPlace> ?c.
?c <http://xmlns.com/foaf/0.1/name> "York"@en.
}
As you can see when you open the fragment in your browser,
there is a form that allows to retrieve triple fragments.
So for each of the 3 triple patterns in the above query,
corresponding fragments are retrieved through the form.
The fragment with the smallest resultset is used to solve subqueries.
This process is then repeated to solve the entire query;
all while following hypermedia controls at each step.
You can see this hypermedia step happen here:
https://github.com/LinkedDataFragments/Client/blob/85b67be35/lib/LinkedData=
FragmentsClient.js#L33
Have a look at the high-level algorithm here:
http://ruben.verborgh.org/blog/2014/03/11/towards-web-scale-web-querying/#q=
uerying-with-linked-data-fragments
Detailed algorithm:
http://linkeddatafragments.org/publications/ldow2014.pdf#page=3D5
Hypermedia is crucial for this type of querying,
because we want to be able to query any type of server
without requiring out-of-band knowledge.
Additionally, we don't want to assume that one server has all fragments,
so links on a fragment can target fragments on other servers as well.
The hypermedia formats supported by our server are HTML+RDFa / Turtle / JSO=
N-LD.
The client supports HTML+RDFa and Turtle.
We use the Hydra vocabulary (http://www.w3.org/community/hydra/) to express=
the hypermedia controls in RDF.
The use of Hydra should enable other hypermedia-driven clients to consume f=
ragments as well.
More details on our use of Hydra here: http://lists.w3.org/Archives/Public/=
public-hydra/2014Mar/0051.html
Looking forward to your feedback, and I'm available for comments and questi=
ons.
Best,
Ruben
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<p>Hi hypermedia/REST people,<br>
<br>
You might like our latest hypermedia client implementation.<br>
It solves queries over Linked Data by using hypermedia:<br>
http://client.linkeddatafragments.org/<br>
(Web version of https://github.com/LinkedDataFragments/Client).<br>
<br>
A server offers basic Linked Data Fragments (http://linkeddatafragments.org/);<br>
they are pieces of a dataset, together with metadata and controls.<br>
The collection of fragments forms a hypermedia API.<br>
<br>
The client is given a SPARQL query and one fragment of the dataset.<br>
For instance, we start from the fragment<br>
http://data.linkeddatafragments.org/dbpedia?object=dbpedia%3ABarack_Obama<br>
and the query:<br>
SELECT ?p, ?c WHERE {<br>
?p a <http://dbpedia.org/ontology/Artist>.<br>
?p <http://dbpedia.org/ontology/birthPlace> ?c.<br>
?c <http://xmlns.com/foaf/0.1/name> "York"@en.<br>
}<br>
As you can see when you open the fragment in your browser,<br>
there is a form that allows to retrieve triple fragments.<br>
So for each of the 3 triple patterns in the above query,<br>
corresponding fragments are retrieved through the form.<br>
The fragment with the smallest resultset is used to solve subqueries.<br>
This process is then repeated to solve the entire query;<br>
all while following hypermedia controls at each step.<br>
You can see this hypermedia step happen here:<br>
https://github.com/LinkedDataFragments/Client/blob/85b67be35/lib/LinkedDataFragmentsClient.js#L33<br>
<br>
Have a look at the high-level algorithm here:<br>
http://ruben.verborgh.org/blog/2014/03/11/towards-web-scale-web-querying/#querying-with-linked-data-fragments<br>
Detailed algorithm:<br>
http://linkeddatafragments.org/publications/ldow2014.pdf#page=5<br>
<br>
Hypermedia is crucial for this type of querying,<br>
because we want to be able to query any type of server<br>
without requiring out-of-band knowledge.<br>
Additionally, we don't want to assume that one server has all fragments,<br>
so links on a fragment can target fragments on other servers as well.<br>
<br>
The hypermedia formats supported by our server are HTML+RDFa / Turtle / JSON-LD.<br>
The client supports HTML+RDFa and Turtle.<br>
We use the Hydra vocabulary (http://www.w3.org/community/hydra/) to express the hypermedia controls in RDF.<br>
The use of Hydra should enable other hypermedia-driven clients to consume fragments as well.<br>
More details on our use of Hydra here: http://lists.w3.org/Archives/Public/public-hydra/2014Mar/0051.html<br>
<br>
Looking forward to your feedback, and I'm available for comments and questions.<br>
<br>
Best,<br>
<br>
Ruben</p>
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