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Requirements and configuration for using alternative SPARQL triplestores with LinkedDataHub

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LinkedDataHub is designed to work with any SPARQL 1.1-compatible triplestore that supports the required protocols. While Apache Jena Fuseki is the default backend, you can use alternative triplestores by adding them as services in docker-compose.override.yml (without modifying the default docker-compose.yml). Browse available triplestore products at kgdev.net/products/.

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Requirements

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For a triplestore to work with LinkedDataHub, it must support the following:

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FeatureRequiredDescription
SPARQL 1.1 Query✅ YesThe triplestore must implement the SPARQL 1.1 Query specification
SPARQL 1.1 Update✅ YesThe triplestore must implement the SPARQL 1.1 Update specification for data modifications
Graph Store Protocol (GSP)✅ YesThe triplestore must support the SPARQL 1.1 Graph Store HTTP Protocol for graph-scoped operations.
Dataset-level CRUD protocol⚪ NoSupport for RDF dataset-scoped CRUD operations, supported by stores such as Apache Fuseki. If not available, LinkedDataHub will fall back to graph-scoped GSP operations (slower but functional).
Authentication⚪ NoEither HTTP Basic authentication or Bearer token authentication (or both). See authentication below for configuration details.
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Service configuration

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Services are configured in config/system.trig using three key properties. See the dataspace reference for the full list of service properties.

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sd:endpoint
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The SPARQL Protocol endpoint URI (for SPARQL Query and Update operations)
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Example: <http://qlever-host:7001/>
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a:graphStore
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The Graph Store Protocol endpoint URI (for graph-scoped CRUD operations)
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Example: <http://qlever-host:7001/>
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Required for all triplestores
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a:quadStore
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The quad store endpoint URI (for dataset-level CRUD operations)
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Optional — if omitted, LinkedDataHub will use graph-scoped GSP fallback
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Example: <http://fuseki-host:3030/ds/> (Fuseki-specific)
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GSP fallback mode

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When a:quadStore is not provided, LinkedDataHub automatically uses graph-scoped Graph Store Protocol operations instead. This mode:

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  • Works with triplestores that don't support dataset-level TriG/N-Quads uploads
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  • Loads data graph-by-graph rather than as a complete dataset
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  • Takes longer during bootstrap (more HTTP requests) but is functionally equivalent
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  • Is required for QLever, Tentris, and other GSP-only triplestores
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Authentication

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LinkedDataHub supports two authentication methods for SPARQL services, both configured in secrets/credentials.trig. See the configuration reference for the credentials secret entry.

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HTTP basic authentication

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Configure username and password using the a:authUser and a:authPwd properties:

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@prefix a: <https://w3id.org/atomgraph/core#> .\n\n<urn:linkeddatahub:services/end-user>\n{\n    <urn:linkeddatahub:services/end-user> a:authUser \"username\" ;\n        a:authPwd \"password\" .\n}\n\n<urn:linkeddatahub:services/admin>\n{\n    <urn:linkeddatahub:services/admin> a:authUser \"username\" ;\n        a:authPwd \"password\" .\n}
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Bearer token authentication

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For triplestores that require Bearer token authentication (like QLever), configure the token using the a:authToken property:

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@prefix a: <https://w3id.org/atomgraph/core#> .\n\n<urn:linkeddatahub:services/end-user>\n{\n    <urn:linkeddatahub:services/end-user> a:authToken \"your-bearer-token\" .\n}\n\n<urn:linkeddatahub:services/admin>\n{\n    <urn:linkeddatahub:services/admin> a:authToken \"your-bearer-token\" .\n}
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This file is mounted as a Docker secret and is NOT committed to git (the /secrets folder is gitignored).

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QLever configuration example

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QLever is a high-performance triplestore optimized for text search. Here's how to configure LinkedDataHub to use QLever:

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    Update config/system.trig to point to your QLever instance:

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    @prefix lapp: <https://w3id.org/atomgraph/linkeddatahub/apps#> .\n@prefix a:    <https://w3id.org/atomgraph/core#> .\n@prefix ldt:  <https://www.w3.org/ns/ldt#> .\n@prefix sd:   <http://www.w3.org/ns/sparql-service-description#> .\n@prefix dct:  <http://purl.org/dc/terms/> .\n\n# Admin app - type + service binding\n\n<urn:linkeddatahub:apps/admin>\n{\n    <urn:linkeddatahub:apps/admin> a lapp:AdminApplication ;\n        ldt:service <urn:linkeddatahub:services/admin> .\n}\n\n# Admin service - QLever\n\n<urn:linkeddatahub:services/admin>\n{\n    <urn:linkeddatahub:services/admin> a sd:Service ;\n        dct:title \"LinkedDataHub admin service (QLever)\" ;\n        sd:supportedLanguage sd:SPARQL11Query, sd:SPARQL11Update ;\n        sd:endpoint <http://qlever-host:7001/> ;\n        a:graphStore <http://qlever-host:7001/> .\n        # Note: a:quadStore omitted - QLever uses GSP fallback mode\n}\n\n# End-user app - type + service binding\n\n<urn:linkeddatahub:apps/end-user>\n{\n    <urn:linkeddatahub:apps/end-user> a lapp:EndUserApplication ;\n        ldt:service <urn:linkeddatahub:services/end-user> .\n}\n\n# End-user service - QLever\n\n<urn:linkeddatahub:services/end-user>\n{\n    <urn:linkeddatahub:services/end-user> a sd:Service ;\n        dct:title \"LinkedDataHub service (QLever)\" ;\n        sd:supportedLanguage sd:SPARQL11Query, sd:SPARQL11Update ;\n        sd:endpoint <http://qlever-host:7001/> ;\n        a:graphStore <http://qlever-host:7001/> .\n        # Note: a:quadStore omitted - QLever uses GSP fallback mode\n}
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    The a:quadStore property is omitted because QLever does not support dataset-level TriG/N-Quads uploads. LinkedDataHub will automatically fall back to using graph-scoped Graph Store Protocol operations (see service configuration).

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    Configure Bearer token authentication (QLever requires this for write operations):

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    Create secrets/credentials.trig with your QLever access token:

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    @prefix a: <https://w3id.org/atomgraph/core#> .\n\n<urn:linkeddatahub:services/end-user>\n{\n    <urn:linkeddatahub:services/end-user> a:authToken \"your-qlever-bearer-token\" .\n}\n\n<urn:linkeddatahub:services/admin>\n{\n    <urn:linkeddatahub:services/admin> a:authToken \"your-qlever-bearer-token\" .\n}
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    See bearer token authentication for details.

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    Uncomment the credentials secret in docker-compose.yml:

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    services:\n  linkeddatahub:\n    secrets:\n      # ... other secrets ...\n      - credentials  # Uncomment this line
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    Start LinkedDataHub:

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    docker-compose up --build
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    During bootstrap, LinkedDataHub will load the default datasets using graph-scoped GSP operations. This takes longer than quad store mode but is functionally equivalent.

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Troubleshooting

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Bootstrap fails with HTTP 400 \"application/trig not supported\"
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Your triplestore doesn't support dataset-level uploads. Remove the a:quadStore property from your service configuration to use GSP fallback mode.
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Bootstrap fails with HTTP 401 or 403
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Check your authentication configuration. Both Bearer token and HTTP Basic auth are configured in secrets/credentials.trig. See authentication for details.
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Queries work but data import fails
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Ensure your triplestore supports SPARQL 1.1 Update and Graph Store Protocol, not just Query. Check the triplestore requirements.
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Connection refused errors
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Check that the endpoint URLs are reachable from the LinkedDataHub Docker container. If running QLever in Kubernetes, use port-forwarding or set up proper networking.
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For more details, see GitHub issue #272 which documents the QLever integration process.

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"^^ . a ; ; "2026-06-16T20:33:55.172Z"^^; ; "Requirements and configuration for using alternative SPARQL triplestores with LinkedDataHub"; "Triplestores"; ; .