Extract subset

Extracts a subset of RDF data from a SPARQL endpoint by querying instances of a specified class and recursively following URI references. Outputs the result in N-Quads format.

Usage

uv run python -m oc_meta.run.migration.extract_subset [options]

Parameters

Parameter	Required	Default	Description
--endpoint	No	http://localhost:8890/sparql	SPARQL endpoint URL
--class	No	http://purl.org/spar/fabio/Expression	Class URI to extract instances of (mutually exclusive with --predicate)
--predicate	No	-	Predicate URI for entity discovery (mutually exclusive with --class)
--limit	No	1000	Maximum number of initial entities
--output	No	output.nq	Output file name
--compress	No	False	Compress output with gzip
--retries	No	5	Maximum retries for failed queries
--no-graphs	No	False	Disable named graph queries and output N-Triples instead of N-Quads
--no-recurse	No	False	Do not recursively follow URI objects

Process

1. Queries the endpoint for subjects that are instances of the specified class
2. For each entity, fetches all triples where it appears as subject
3. Recursively processes any URI found as object
4. Serializes the collected data as N-Quads

Example

Extract 500 bibliographic resources with their related entities:

uv run python -m oc_meta.run.migration.extract_subset \
    --endpoint http://localhost:8890/sparql \
    --class http://purl.org/spar/fabio/Expression \
    --limit 500 \
    --output subset.nq.gz \
    --compress

Use cases

• Create test datasets from production data
• Extract samples for debugging
• Migrate specific portions of a triplestore