Small example of SPARQL wrapping in Prova

Guys,
 
A short update about the SPARQL integration ongoing for the Prova
language (prova.ws). It may be used in an upcoming Betfair RIF use case.
 
A new CVS update introduces SPARQL querying mapped to a built-in
predicate. The functionality is based on Jena 2.4 ARQ library. The new
built-in sparql_select predicate does the job. The predicate is
non-deterministic, iterating over one binding (solution) at a time. Here
is an example: 
Code:	
% Goal
:- eval(ex059()). 

ex059() :- 
   QueryString = ' 
      PREFIX foaf: <http://xmlns.com/foaf/0.1/> 
      PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> 
      SELECT ?contributor ?url ?type 
         FROM <http://planetrdf.com/bloggers.rdf> 
         WHERE { 
            ?contributor foaf:name "Bob DuCharme" . 
            ?contributor foaf:weblog ?url . 
            ?contributor rdf:type ?type . 
         } 
   ', 
   sparql_select(QueryString,url(URL),type(Type)|X), 
   println([[url,URL],[type,Type]|X],","). 
% Prints: 
%
["url",http://www.snee.com/bobdc.blog/],["type",http://xmlns.com/foaf/0.
1/Agent],["contributor",72260fc5:10c1027fc9f:-7fef] 
%
["url",http://www.snee.com/bobdc.blog/],["type",http://xmlns.com/foaf/0.
1/Person],["contributor",72260fc5:10c1027fc9f:-7fef] 



Note that the predicate requires only one parameter, a query string
expressed in the SPARQL language. In this case, the actual data will be
assumed to be taken from FROM clause. A Jena Model can also be used as a
first parameter, in which case the FROM clause is not needed (see the
full example ex059.prova). The other arguments of the predicate include
name(value) pairs where names are the names of the variables that are
returned from the query. The names are assumed to be constant. However,
you can also supply a list tail (rest) that will return all name(value)
pairs in the resulting binding as a list. If no name(value) pairs and no
rest are supplied, the predicate succeeds only if there are matches in
the target graph(s).

Alex Kozlenkov
 
Advanced Technologies Group
www.betfair.com <http://www.betfair.com>

Received on Monday, 26 June 2006 12:23:05 UTC