On 09/03/14 22:24, Cong Wang wrote:
Hi everybody,
My name is Cong Wang, currently a Ph.D student at Wright State University
with Pascal Hitzler. I am very interested two ideas, "Generate JSON from
SPARQL directly" and "Define SPARQL commands in Jena rules". I have several
questions regarding the two topics.
For "Generate JSON from SPARQL directly",
Is that you want translate sparql query into json format, such that we can
use it to query json data? Since under W3C recommendation, there's way to
translate sparql results into json [1]. The only missing part is converting
sparql query with json query. But even if so, I'm still not sure the
significance. What's the motivation here?
As things currently stand, there isn't a volunteer mentor for this project.
The idea is to produce application-specific JSON under the control of
some template system, whether that's application-specific idiomatic JSON
or JSON-LD. The standard result format is already supported and well
used - it encodes a result set in JSON with all the RDF details showing.
For "Define SPARQL commands in Jena rules",
I remember there's a paper by Axel Polleres [2]. It's about translating
SPARQL into datalog. Although datalog is arbitrary variables and Jena rules
is only 3 variables, there should be a way to convert.
But I don't quite understand how it can "increase the expressiveness of
Jena". In principle, SPARQL is just indexing, and Jena rules actually have
already indexed the triples while grounding variables.
On a technical level, SPARQL can say things the rules can't, or can only
in a complex way. GROUP BY and aggregation for example.
On a deployment level, users know SPARQL syntax so being able to connect
that knowledge to the rules would be good. The SPARQL engine also has a
quite extensive collection of XSD operations.
Andy
[1]. http://www.w3.org/TR/sparql11-results-json/
[2]. Axel Polleres: From SPARQL to rules (and back). WWW 2007
Best regards.
