I am trying to build a subgraph of freebase based on a given topic entity, as the time taken to query the full freebase is too time consuming.
My first attempt at building a 3-hop subgraph was as follows:
PREFIX ns:<http://rdf.freebase.com/ns/>
SELECT ?r0, ?e1, ?r1, ?e2, ?r2, ?e3 WHERE
{
ns:m.034rd ?r0 ?e1.
?e1 ?r1 ?e2.
?e2 ?r2 ?e3.
}
This does not work, as it ignores all paths which are max 1- and 2- Hops away from the topic entity.
The Next attempt I made was as follows:
PREFIX ns:<http://rdf.freebase.com/ns/>
SELECT ?r0, ?e1, ?r1, ?e2, ?r2, ?e3 WHERE
{
ns:m.034rd ?r0 ?e1.
OPTIONAL{
?e1 ?r1 ?e2.
}
OPTIONAL{
?e2 ?r2 ?e3.
}
}
This did not work either, although I admittedly don't know why or if I am even using the OPTIONAL tag correctly.
Following my failure to build a single SPARQL query, I tried to iteratively query freebase, and build the graph as such. I have tried two things:
(1):
PREFIX ns:<http://rdf.freebase.com/ns/>
SELECT ?r0, ?e1 WHERE
{
ns:m.034rd ?r0 ?e1.
}
and
PREFIX ns:<http://rdf.freebase.com/ns/>
SELECT ?r0, ?e1, ?r1, ?e2 WHERE
{
ns:m.034rd ?r0 ?e1.
?e1 ?r1 ?e2.
}
and
PREFIX ns:<http://rdf.freebase.com/ns/>
SELECT ?r0, ?e1, ?r1, ?e2, ?r2, ?e3 WHERE
{
ns:m.034rd ?r0 ?e1.
?e1 ?r1 ?e2.
?e2 ?r2 ?e3.
}
I had assumed that doing this would provide me with all paths (1-, 2-, and 3-Hops) stemming from the topic entity.
(2) :
PREFIX ns:<http://rdf.freebase.com/ns/>
SELECT ?r0, ?e1 WHERE
{
e0 ?r0 ?e1.
}
where e0 was initially set to the topic entity. Following which the above query was run for each e1 returned by the initial query. This process was repeated 3 times (3-Hops).
I am still no closer to finding the correct way to build the subgraph and any help would be greatly appreciated.
