What are packages?

A LinkedDataHub package is a reusable component that bundles together a vocabulary ontology and XSLT templates into a single installable unit. Packages enable:

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• Rapid application setup with pre-configured domain vocabularies
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• Sharing and reusing common vocabulary definitions
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• Custom rendering for vocabulary-specific resources
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• Modular extension of dataspace functionality
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Package structure

Each package consists of two files:

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ns.ttl — Package ontology

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An RDF ontology file that imports the external vocabulary using owl:imports and attaches blocks to properties using ldh:view (forward relationships) or ldh:inverseView (inverse relationships). Blocks are typically ldh:View resources with SPARQL queries that render related data for property values.

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layout.xsl — XSLT stylesheet

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XSLT transformation file with templates that override default rendering using system modes like bs2:* (Bootstrap 2.3.2 components) and xhtml:* (XHTML elements). See Stylesheets reference for details on XSLT customization.

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Package files are organized in the LinkedDataHub-Apps repository:

packages/\n├── package-name/\n│   ├── ns.ttl         # Ontology with views\n│   └── layout.xsl     # XSLT stylesheet

Package metadata is published as Linked Data that resolves from the package URI (e.g., https://packages.linkeddatahub.com/skos/#this).

Package metadata

Package metadata is published as Linked Data that resolves from the package URI using standard LinkedDataHub properties:

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lapp:Package

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The RDF class for package descriptors

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rdfs:label

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Human-readable package name

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dct:description

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Package description and purpose

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ldt:ontology

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Points to the package ontology URI (from LDT vocabulary)

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ac:stylesheet

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Points to the package stylesheet URI (from AtomGraph Client vocabulary)

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Example package metadata:

@prefix lapp: <https://w3id.org/atomgraph/linkeddatahub/apps#> .\n@prefix ldt:  <https://www.w3.org/ns/ldt#> .\n@prefix ac:   <https://w3id.org/atomgraph/client#> .\n\n<https://packages.linkeddatahub.com/skos/#this> a lapp:Package ;\n    rdfs:label \"SKOS Package\" ;\n    dct:description \"SKOS vocabulary support with custom templates\" ;\n    ldt:ontology <https://raw.githubusercontent.com/AtomGraph/LinkedDataHub-Apps/master/packages/skos/ns.ttl#> ;\n    ac:stylesheet <https://raw.githubusercontent.com/AtomGraph/LinkedDataHub-Apps/master/packages/skos/layout.xsl> .

Package ontology

The package ontology file contains two layers:

Vocabulary import

Imports the external vocabulary using owl:imports. See Ontologies reference for ontology management details.

<https://raw.githubusercontent.com/AtomGraph/LinkedDataHub-Apps/master/packages/skos/ns.ttl#> a owl:Ontology ;\n    owl:imports <http://www.w3.org/2004/02/skos/core> .

Property views

SPARQL-based views attached to properties from the imported vocabulary:

skos:narrower ldh:view ns:NarrowerConcepts .\n\nns:NarrowerConcepts a ldh:View ;\n    dct:title \"Narrower concepts\" ;\n    spin:query ns:SelectNarrowerConcepts .\n\nns:SelectNarrowerConcepts a sp:Select ;\n    sp:text \"\"\"SELECT DISTINCT ?narrower\n    WHERE { GRAPH ?graph { $about skos:narrower ?narrower } }\n    ORDER BY ?narrower\"\"\" .

Views are rendered when displaying resources that have the specified property. Use ldh:view for forward relationships (resource has property) or ldh:inverseView for inverse relationships (other resources point to this resource via property).

Package stylesheet

XSLT templates using system modes to override default rendering:

<!-- Hide properties from default property list -->\n<xsl:template match=\"skos:narrower | skos:broader\" mode=\"bs2:PropertyList\"/>\n\n<!-- Override XHTML head elements -->\n<xsl:template match=\"*\" mode=\"xhtml:Style\">\n    <!-- Custom styles -->\n</xsl:template>

Available system modes include:

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• bs2:* — Bootstrap 2.3.2 components (PropertyList, Form, etc.)
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• xhtml:* — XHTML elements (Style, Script, etc.)
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• Additional modes documented in the Stylesheets reference
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Installing packages

Installation requires Control access to the administration application. See the step-by-step installation guide for detailed instructions.

Installation will fail if these files do not exist.

Installation process

When you install a package, the system performs the following steps:

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1. Fetches package metadata from the package URI
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2. Hashes the package ontology URI using SHA-1 to create a unique document slug
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3. Downloads package ontology (ns.ttl) and PUTs it as a document to ${admin_base}ontologies/{hash}/ where {hash} is the SHA-1 hash of the ontology URI
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4. Adds owl:imports from the namespace ontology to the package ontology in the namespace graph (${admin_base}ontologies/namespace/)
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5. Clears and reloads the namespace ontology from cache to pick up the new imports
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6. Downloads package stylesheet (layout.xsl) and saves it to /static/{package-path}/layout.xsl where {package-path} is derived from the package URI (e.g., com/linkeddatahub/packages/skos/ for https://packages.linkeddatahub.com/skos/)
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7. Updates master stylesheet at /static/xsl/layout.xsl by adding import:\n

   <xsl:import href=\"../com/atomgraph/linkeddatahub/xsl/bootstrap/2.3.2/layout.xsl\"/>  <!-- System -->\n<xsl:import href=\"../com/linkeddatahub/packages/skos/layout.xsl\"/>  <!-- Package (added) -->

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docker-compose restart linkeddatahub

Uninstalling packages

Packages can be safely uninstalled, which removes:

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• Package ontology imports from the application
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• Package-specific data and resources
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• Associated queries and stylesheets
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Architecture

Installation-time vs runtime

Packages use installation-time composition, NOT runtime composition:

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• ✅ Package content is integrated during installation (via JAX-RS endpoints)
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• ✅ Ontology and XSLT are pre-composed before being loaded
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• ✅ No runtime overhead
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• ❌ No dynamic package loading at request time
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HTTP endpoints

Package installation and uninstallation is performed via system endpoints on the admin application. See packages/install and packages/uninstall in the HTTP API reference.

File system structure

After installing the SKOS package:

webapp/\n├── static/\n│   ├── com/\n│   │   └── linkeddatahub/\n│   │       └── packages/\n│   │           └── skos/\n│   │               └── layout.xsl          # Package stylesheet\n│   └── xsl/\n│       ├── layout.xsl                      # End-user master stylesheet\n│       └── admin/\n│           └── layout.xsl                  # Admin master stylesheet

Creating custom packages

Developers can create custom packages for their own domain vocabularies. The process involves:

Write package ontology

Create ns.ttl with vocabulary import and views:

<https://raw.githubusercontent.com/you/repo/master/packages/schema.org/ns.ttl#> a owl:Ontology ;\n    owl:imports <http://schema.org/> .\n\n# Attach view to a property\nschema:knows ldh:view :PersonKnows .\n\n:PersonKnows a ldh:View ;\n    dct:title \"Knows\" ;\n    spin:query :SelectPersonKnows .\n\n:SelectPersonKnows a sp:Select ;\n    sp:text \"\"\"\n    SELECT DISTINCT ?person\n    WHERE { GRAPH ?graph { $about schema:knows ?person } }\n    ORDER BY ?person\n    \"\"\" .

Write XSLT stylesheet

Create layout.xsl with XSLT templates using system modes like bs2:* and xhtml:*. See the Stylesheets reference for template customization patterns.

<xsl:template match=\"schema:knows\" mode=\"bs2:PropertyList\"/>

Publish package metadata

Publish package metadata as Linked Data at your package URI:

<https://packages.linkeddatahub.com/schema.org/#this> a lapp:Package ;\n    rdfs:label \"Schema.org Package\" ;\n    dct:description \"Schema.org vocabulary support\" ;\n    ldt:ontology <https://raw.githubusercontent.com/you/repo/master/packages/schema.org/ns.ttl#> ;\n    ac:stylesheet <https://raw.githubusercontent.com/you/repo/master/packages/schema.org/layout.xsl> .

Ensure the metadata contains ldt:ontology and ac:stylesheet properties pointing to the package resources.

Test installation

Use the CLI to test your package installation:

install-package.sh \\\n  -b \"https://localhost:4443/\" \\\n  -f ssl/owner/cert.pem \\\n  -p \"$cert_password\" \\\n  --package \"https://packages.linkeddatahub.com/schema.org/#this\"

Available packages

A curated list of available packages can be found in the LinkedDataHub-Apps repository. Each package directory contains the package ontology (ns.ttl) and stylesheet (layout.xsl) files.