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Structure

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The default LinkedDataHub dataset structure follows these conventions:

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1. The default graph is not used.
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2. Each document's description is stored in an RDF named graph whose name is the same as the document URI. The graph can be managed using the Graph Store Protocol.
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3. Documents form a parent/child hierarchy. There are two types of documents: containers, which can have other documents as children, and items, which cannot.
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The default dataset is installed into a dataspace service during setup.

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In TriG, the Northwind Beverages category document — one named graph, named by the document URI, holding the document's whole description:

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<https://localhost:4443/categories/1/>\n{\n    <https://localhost:4443/categories/1/> a dh:Item ;\n        dct:title \"Beverages\" ;\n        sioc:has_container <https://localhost:4443/categories/> ;\n        foaf:primaryTopic <https://localhost:4443/categories/1/#this> .\n\n    <https://localhost:4443/categories/1/#this> a schema:ProductGroup ;\n        schema:name \"Beverages\" ;\n        schema:identifier \"1\" .\n}

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Live: /categories/1/

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Hierarchical URIs

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By default, the URIs of the document resources represent the same parent/child hierarchy: the root container's URI equals the dataspace's base URI,\n and descendant document URIs are relative to their parent container's.

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https://localhost:4443/                    # root container = the base URI\nhttps://localhost:4443/categories/         # its child container\nhttps://localhost:4443/categories/1/       # an item in the container\nhttps://localhost:4443/categories/1/#this  # the category itself — a fragment of its document

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Uploaded files are an exception to this rule. They are content-addressed in the uploads/{sha1sum} namespace, where sha1sum is the SHA1 hash of the file content — the Beverages\n image, for example, lives at uploads/ec56b79671b30ecb98316d9b766fba198286b3b6 no matter which document references it.

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Default datasets

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The default datasets of administration and end-user dataspaces can be found in platform/datasets/admin.trig and\n platform/datasets/end-user.trig, respectively.

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The end-user dataset contains the root container document and descriptions of the public DBpedia and Wikidata SPARQL services. The administration dataset contains the root container,\n the sign-up and ontology-clearing endpoint documents, the acl/ document tree — containers for agents, public keys, users, groups,\n authorization requests and authorizations, the default authorizations, and the owners, writers and readers groups — as well as the ontologies/ container.

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RDF terms (classes, properties etc.) used in the default datasets come from the well-known FOAF and SIOC vocabularies (with additional LinkedDataHub-specific assertions) as well as system ontologies.

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Storage

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The dataset of each dataspace is stored in an RDF triplestore which is accessed as a SPARQL service. End-user dataspaces and admin dataspaces have separate datasets and are backed by two different services.

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The default triplestore is Apache Jena Fuseki, and multiple dataspaces can share the same backend service.\n See the triplestores reference for compatibility requirements and configuration examples.

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