Parameterised SPARQL

Every serious SPARQL client offers a parameter API:

• Apache Jena: ParameterizedSparqlString
• rdflib (Python): prepareQuery + initBindings={...}
• Stardog / GraphDB: typed bind variables

The library quotes, escapes and types the value, so a literal stays a literal and an IRI stays an IRI.

User input becomes a typed RDF term before it touches the query string.

Worked example — a parameterised SELECT.

You write the query with a variable where the dynamic value will go. The application supplies the value at call time:

# Your query template (saved as a string, no concatenation):
PREFIX : <http://example.org/>
SELECT ?book WHERE {
  ?book :author ?author .
}

# Python (rdflib) — the library binds ?author for you:
from rdflib import Literal
from rdflib.plugins.sparql import prepareQuery

q = prepareQuery(QUERY_STRING)
results = graph.query(q, initBindings={'author': Literal('Alice')})

What the library does for you:

1. Quotes & escapes the value.
2. Tags it with the right datatype (here xsd:string).
3. Substitutes it into the query as a typed RDF term.

Same query template, different bindings each call — the SemWeb equivalent of a SQL prepared statement. Below, write just the SPARQL template; the grader assumes ?author is bound by the host application.