A problem with querying a graph with SPARQL on Bioportal - sparql

Question

I am querying an ontology on the Bioportal endpoint. The ontology (NIF) is stored as a graph, so I put it in the FROM clause as the endpoint instructed.
SELECT DISTINCT ?p
FROM <http://bioportal.bioontology.org/ontologies/NIF>
WHERE{
?p a rdf:Property
}
limit 100
However, as can be seen below, the results came back showing few properties related to NIF and others to a different ontology called SKOS (Simple Knowledge Organization System).
In the Bioportal documentation it is said it maps some properties to SKOS properties, so I thought maybe the results are fine.
However, I had to test if I am querying the correct graph. So I used the below code to count the number of nodes since I know the NIF has around 3.6 million triples!
SELECT (count (*) as ?nodes)
FROM <http://bioportal.bioontology.org/ontologies/NIF>
WHERE{
?s ?p ?o
}
This resulted in 7984 nodes with and without the FROM clause! So I guessed I should be using the "count" incorrectly!
So I wonder how I should make sure that I am just querying the NIF ontology. Also, how to count its nodes?
Thanks :)

Answer 1

Try using SERVICE keyword.
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
SELECT (count (*) as ?nodes)
WHERE
{
SERVICE <http://bioportal.bioontology.org/ontologies/NIF>
{
?s ?p ?o
}
}
If this fails, possibly the service you are connecting is not correct or up.
Try below example which connects to DBpedia:
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
SELECT (count (*) as ?nodes)
WHERE
{
SERVICE <http://DBpedia.org/sparql>
{
?s ?p ?o
}
}
By the way I can;t access URL http://bioportal.bioontology.org/ontologies/NIF. Seems to be unavailable or down.