SPARQL Guide

SPARQL is a query language used to retrieve and manipulate data stored in RDF format. JudaicaLink provides a public SPARQL endpoint that allows users to query the JudaicaLink knowledge graph.

SPARQL Endpoint

JudaicaLink’s SPARQL endpoint is accessible at:

URL: https://data.judaicalink.org/sparql.html

You can use this endpoint to run queries directly via a web interface or programmatically using command-line tools or programming languages.

Basic SPARQL Query Structure

A SPARQL query consists of:

SELECT Clause: Specifies the variables to retrieve.
WHERE Clause: Defines the conditions that must be met.
LIMIT/OFFSET: Restricts the number of results.

Example Query

Retrieve the first 10 persons in the dataset:

SELECT ?person ?name WHERE {
    ?person a <http://xmlns.com/foaf/0.1/Person> ;
            <http://xmlns.com/foaf/0.1/name> ?name .
} LIMIT 10

Filtering Results

Filter results using conditions like strings, numbers, or dates:

SELECT ?person ?name WHERE {
    ?person a <http://xmlns.com/foaf/0.1/Person> ;
            <http://xmlns.com/foaf/0.1/name> ?name .
    FILTER regex(?name, "Moses", "i")
}

Sorting and Ordering Results

Use ORDER BY to sort results:

SELECT ?person ?name WHERE {
    ?person a <http://xmlns.com/foaf/0.1/Person> ;
            <http://xmlns.com/foaf/0.1/name> ?name .
} ORDER BY ?name

Querying with Optional Data

Use OPTIONAL to include additional data if available:

SELECT ?person ?name ?birthdate WHERE {
    ?person a <http://xmlns.com/foaf/0.1/Person> ;
            <http://xmlns.com/foaf/0.1/name> ?name .
    OPTIONAL { ?person <http://dbpedia.org/ontology/birthDate> ?birthdate }
}

Accessing SPARQL Programmatically

Use cURL to send SPARQL queries:

curl -G --data-urlencode "query=SELECT * WHERE { ?s ?p ?o } LIMIT 10" \
-H "Accept: application/sparql-results+json" https://data.judaicalink.org/sparql

Use Python with rdflib:

from rdflib import Graph

g = Graph()
g.parse("https://data.judaicalink.org/sparql", format="xml")

for s, p, o in g:
    print(s, p, o)

Troubleshooting & Support

Query returning no results? Ensure the dataset contains relevant data.
SPARQL syntax errors? Validate your query using a SPARQL validator.
Need help? Contact us at https://labs.judaicalink.org/contact/

— JudaicaLink’s SPARQL endpoint allows for rich, structured data retrieval. Start exploring now! 🚀