ASK queries

ASK queries test whether a pattern exists in the data and return a boolean result directly.

Basic ASK query

from sparqlite import SPARQLClient

with SPARQLClient("https://opencitations.net/meta/sparql") as client:
    # Check if a specific DOI exists in OpenCitations
    exists = client.ask("""
        PREFIX datacite: <http://purl.org/spar/datacite/>
        PREFIX literal: <http://www.essepuntato.it/2010/06/literalreification/>

        ASK {
            ?id datacite:usesIdentifierScheme datacite:doi ;
                literal:hasLiteralValue "10.1162/qss_a_00023" .
        }
    """)

    if exists:
        print("This DOI exists in OpenCitations!")
    else:
        print("DOI not found")

Using the boolean result

The ask() method returns True or False directly:

with SPARQLClient("https://opencitations.net/meta/sparql") as client:
    result = client.ask("""
        PREFIX fabio: <http://purl.org/spar/fabio/>

        ASK {
            ?article a fabio:JournalArticle .
        }
    """)

    # Use directly in conditionals
    if result:
        print("There are journal articles in the database")

    # result is already a bool
    print(f"Result type: {type(result)}")  # <class 'bool'>

Checking data existence

ASK queries are useful for validation before executing more complex queries:

with SPARQLClient("https://opencitations.net/meta/sparql") as client:
    # Check if a DOI exists before querying article details
    doi = "10.1162/qss_a_00023"

    exists = client.ask(f"""
        PREFIX datacite: <http://purl.org/spar/datacite/>
        PREFIX literal: <http://www.essepuntato.it/2010/06/literalreification/>

        ASK {{
            ?id datacite:usesIdentifierScheme datacite:doi ;
                literal:hasLiteralValue "{doi}" .
        }}
    """)

    if exists:
        result = client.query(f"""
            PREFIX fabio: <http://purl.org/spar/fabio/>
            PREFIX dcterms: <http://purl.org/dc/terms/>
            PREFIX datacite: <http://purl.org/spar/datacite/>
            PREFIX literal: <http://www.essepuntato.it/2010/06/literalreification/>

            SELECT ?article ?title WHERE {{
                ?article a fabio:JournalArticle ;
                         dcterms:title ?title ;
                         datacite:hasIdentifier ?id .
                ?id datacite:usesIdentifierScheme datacite:doi ;
                    literal:hasLiteralValue "{doi}" .
            }}
        """)
        for row in result["results"]["bindings"]:
            print(f"Found article: {row['title']['value']}")
    else:
        print(f"DOI {doi} not found in OpenCitations")