Extract subset

Extracts a subset of RDF data from a SPARQL endpoint by querying instances of a specified class (or from a file of entity URIs) and recursively following URI references. Outputs the result in N-Quads or N-Triples 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 --entities-file)
--entities-file	No	-	File with entity URIs to extract, one per line (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

Process

1. Discovers entities by querying instances of a class, or loads them from a file
2. For each entity, fetches all triples (or quads) where it appears as subject
3. Recursively processes any URI found as object
4. Serializes the collected data as N-Quads (default) or N-Triples (--no-graphs)

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