Computing Recursive SPARQL Queries

Introducing Recursion in SPARQL

We developed a SPARQL function called wfn:runSPARQL that takes as a parameter a string containing a SPARQL query and executes it. Such SPARQL query can refer to itself, enabling recursion and the use of any Turing-computable function within SPARQL.

Our work can be found in: Computing Recursive SPARQL Queries. Atzori M. 8th IEEE International Conference on Semantic Computing (2014)

Name space and Public Endpoint

Officially, we plan to use the following namespace:

wfn: <http://webofcode.org/wfn/>

In order to experiment it, we published an endpoint implmenting our wfn:runSPARQL function, available at:

http://swipe.unica.it/ jena/sparql

An Example: Computing the Factorial

The following is an example of recursive SPARQL query that computes the factorial of 3:

PREFIX wfn: <http://webofcode.org/wfn/>
SELECT ?result 
{ 
        # bind variables to parameter values 
        VALUES (?query ?endpoint) { ( 
                "BIND ( IF(?i0 <= 0, 1, ?i0 * wfn:runSPARQL(?query,?endpoint, ?i0 -1)) AS ?result)" 
                "http://swipe.unica.it/jena/sparql"
        )}
   
        # actual call of the recursive query 
        BIND( wfn:runSPARQL(?query,?endpoint,3) AS ?result)
} 

It can be queried against our endpoint above, or using the web interface at:

http://swipe.unica.it/ jena/sparql.html

Publications

1. Computing Recursive SPARQL Queries. Atzori M. 8th IEEE International Conference on Semantic Computing (2014)