SPARQL.md

SPARQL

SPARQL Protocol and RDF Query Language — the W3C standard query and update language for [[RDF]] data.

In Flexo MMS

The Layer 1 service requires a SPARQL 1.1 compliant [[quadstore]] as a backend (Layer 1 docs). The reference stack uses [[Apache Jena Fuseki]], which exposes three HTTP endpoints (flexo-mms-layer1-service):

Endpoint	Fuseki path	Flexo env var
SPARQL Query	/ds/sparql	FLEXO_MMS_QUERY_URL
SPARQL Update	/ds/update	FLEXO_MMS_UPDATE_URL
[[Graph Store Protocol]]	/ds/data	FLEXO_MMS_GRAPH_STORE_PROTOCOL_URL

For production deployments, read and write operations can be separated to distinct backend nodes using FLEXO_MMS_MASTER_QUERY_URL for strict consistency reads (Layer 1 docs).

Cross-Commit Queries

Named graphs enable queries scoped to a specific commit snapshot:

SELECT ?element ?name
WHERE {
    GRAPH <urn:mms:snapshot:commit-abc123> {
        ?element a sysml:PartDefinition ;
                 sysml:name ?name .
    }
}

They also enable cross-commit comparisons — effectively querying the diff between two model states:

# Elements present in the new commit but absent from the old
SELECT ?element
WHERE {
    GRAPH <urn:mms:snapshot:commit-new> {
        ?element a sysml:Element .
    }
    FILTER NOT EXISTS {
        GRAPH <urn:mms:snapshot:commit-old> {
            ?element a sysml:Element .
        }
    }
}

This pattern complements the [[Diff and Delta|diff service]] — the diff service computes and stores deltas as SPARQL UPDATE patches, while cross-commit queries allow ad-hoc comparison without pre-computed deltas.

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