Common Vocabulary Bundles: DCTERMS, Schema.org, and FOAF

This cookbook chapter shows how to load and use the three most widely-deployed linked-data vocabularies in pg_ripple — Dublin Core Terms (DCTERMS), Schema.org, and FOAF — using the named bundle API introduced in v0.98.0.

Together with SKOS (v0.98.0), these bundles complete the "Big 5" vocabularies that cover the vast majority of real-world knowledge-graph interoperability.

Why These Vocabularies?

VocabularyNamespace prefixTypical use
Dublin Core Termsdcterms:Metadata — creator, date, subject, rights, format
Schema.orgschema:Structured data — people, orgs, products, places, events
FOAFfoaf:Social-graph data — persons, accounts, social connections

All three are already used in billions of public RDF documents, Wikidata exports, and enterprise knowledge graphs. Loading their rule sets lets pg_ripple perform property-hierarchy inference, type-subsumption reasoning, and integrity validation over data you already have — without any schema changes.

Loading the Bundles

-- DCTERMS: 11 Datalog rules + 8 integrity validators
SELECT pg_ripple.load_datalog_bundle('dcterms');
SELECT pg_ripple.load_shape_bundle('dcterms-integrity');

-- Schema.org: 15 Datalog rules + 6 integrity validators
SELECT pg_ripple.load_datalog_bundle('schema');
SELECT pg_ripple.load_shape_bundle('schema-integrity');

-- FOAF: 8 Datalog rules + 5 integrity validators
SELECT pg_ripple.load_datalog_bundle('foaf');
SELECT pg_ripple.load_shape_bundle('foaf-integrity');

After loading, confirm activation:

SELECT bundle_name, bundle_version, activated_at
FROM pg_ripple.active_datalog_bundles
ORDER BY activated_at;

DCTERMS — Dublin Core Terms

Inferred Properties

The dcterms bundle adds 11 rules, including:

  • DC11 compatibility aliases — dc11:title is treated equivalently to dcterms:title, and similarly for creator, subject, description, publisher, date, type, format, identifier, source, language.
  • Structural inverses — dcterms:hasPart ↔ dcterms:isPartOf, dcterms:hasVersion ↔ dcterms:isVersionOf, dcterms:replaces ↔ dcterms:isReplacedBy.
  • DC-SKOS bridge (DC-SKOS-01) — resources whose dcterms:subject is a member of a SKOS ConceptScheme automatically receive a skos:Concept type assertion.

Example

-- Load some metadata triples using the old dc11: namespace.
SELECT pg_ripple.load_turtle($$
@prefix dc11: <http://purl.org/dc/elements/1.1/> .
@prefix dcterms: <http://purl.org/dc/terms/> .
@prefix ex: <https://example.org/> .

ex:Article1 dc11:creator "Alice" ;
            dcterms:hasPart ex:Section1 .
$$);

-- Load the dcterms rule set.
SELECT pg_ripple.load_datalog_bundle('dcterms');

-- dc11:creator is now mapped to dcterms:creator.
SELECT pg_ripple.sparql_select($$
  SELECT ?article ?creator
  WHERE { ?article <http://purl.org/dc/terms/creator> ?creator }
$$);

-- dcterms:isPartOf is inferred from dcterms:hasPart.
SELECT pg_ripple.sparql_select($$
  SELECT ?part ?whole
  WHERE { ?part <http://purl.org/dc/terms/isPartOf> ?whole }
$$);

Schema.org — Structured Data Vocabulary

Inferred Properties

The schema bundle adds 15 rules:

  • Inverse pairs — schema:subjectOf ↔ schema:about, schema:hasPart ↔ schema:isPartOf, schema:workExample ↔ schema:exampleOfWork, schema:member ↔ schema:memberOf.
  • Type hierarchy — schema:LocalBusiness ⊆ schema:Organization ⊆ schema:Thing, schema:Person ⊆ schema:Thing, schema:Product ⊆ schema:Thing, and several more.
  • Cross-vocab bridges — schema:author → foaf:maker (SCHEMA-FOAF-01), schema:name → dcterms:title (SCHEMA-DC-01), schema:dataset → dcat:Dataset (SCHEMA-DCAT-01).

SQL Helper: schema_type_ancestors

-- Return all Schema.org type ancestors for a given IRI.
SELECT ancestor_type
FROM pg_ripple.schema_type_ancestors('https://schema.org/LocalBusiness');
-- Returns: schema:LocalBusiness, schema:Organization, schema:Thing

Example

-- Load a local business.
SELECT pg_ripple.load_turtle($$
@prefix schema: <https://schema.org/> .
@prefix ex: <https://example.org/> .

ex:AcmeCafe a schema:CafeOrCoffeeShop ;
    schema:name "ACME Café" ;
    schema:address ex:CafeAddress .
$$);

SELECT pg_ripple.load_datalog_bundle('schema');

-- CafeOrCoffeeShop is a FoodEstablishment, LocalBusiness, Organization, Thing.
SELECT pg_ripple.sparql_select($$
  SELECT ?type
  WHERE { <https://example.org/AcmeCafe> a ?type }
  ORDER BY ?type
$$);

FOAF — Friend-of-a-Friend

Inferred Properties

The foaf bundle adds 8 rules:

  • foaf:knows symmetry — if Alice knows Bob, Bob knows Alice.
  • Type subsumption — foaf:Person ⊆ foaf:Agent, foaf:Organization ⊆ foaf:Agent, foaf:Group ⊆ foaf:Agent.
  • Inverse properties — foaf:account ↔ foaf:accountFor, foaf:made ↔ foaf:maker.
  • DC-FOAF bridge (DC-FOAF-01) — dcterms:creator triples generate a corresponding foaf:maker assertion on the referenced resource.

SQL Helper: foaf_persons

-- Return all foaf:Person IRIs and their foaf:name labels.
SELECT person_iri, name_label
FROM pg_ripple.foaf_persons();

Example

-- Load FOAF data.
SELECT pg_ripple.load_turtle($$
@prefix foaf: <http://xmlns.com/foaf/0.1/> .
@prefix ex: <https://example.org/> .

ex:Alice a foaf:Person ;
    foaf:name "Alice" ;
    foaf:knows ex:Bob .
ex:Bob a foaf:Person ;
    foaf:name "Bob" .
$$);

SELECT pg_ripple.load_datalog_bundle('foaf');

-- foaf:knows is symmetric: Bob knows Alice.
SELECT pg_ripple.sparql_select($$
  SELECT ?who ?knows
  WHERE { ?who <http://xmlns.com/foaf/0.1/knows> ?knows }
$$);

-- foaf:Person ⊆ foaf:Agent: Alice is also a foaf:Agent.
SELECT pg_ripple.sparql_select($$
  SELECT ?agent
  WHERE { ?agent a <http://xmlns.com/foaf/0.1/Agent> }
$$);

Cross-Vocabulary Inference

When all three bundles (and SKOS) are loaded together, cross-vocabulary bridges activate:

Rule IDEffect
DC-FOAF-01dcterms:creator ?x → foaf:maker ?x
SCHEMA-FOAF-01schema:author ?x → foaf:maker ?x
SCHEMA-DC-01schema:name ?x → dcterms:title ?x
DC-SKOS-01dcterms:subject ?x where ?x is in a ConceptScheme → ?x a skos:Concept

This means a resource described with schema:author can be found via a foaf:maker query, and a resource with schema:name can be found via a dcterms:title filter — without any data transformation.

Integrity Validation

Each vocabulary ships with a corresponding integrity bundle:

-- Validate DCTERMS constraints (title cardinality, date format, etc.)
SELECT pg_ripple.load_shape_bundle('dcterms-integrity');

-- Validate Schema.org constraints (required name, URL format, price range, etc.)
SELECT pg_ripple.load_shape_bundle('schema-integrity');

-- Validate FOAF constraints (homepage IRI, mbox mailto:, name cardinality)
SELECT pg_ripple.load_shape_bundle('foaf-integrity');

Integrity violations are surfaced through the standard SHACL validation report.

Checking Active Bundles

SELECT bundle_name, bundle_version, activated_at
FROM pg_ripple.active_datalog_bundles
ORDER BY bundle_name;

-- bundle_name         | bundle_version | activated_at
-- --------------------+----------------+---------------------------
-- dcterms             | 0.99.0         | 2026-05-07 10:00:00+00
-- foaf                | 0.99.0         | 2026-05-07 10:00:01+00
-- schema              | 0.99.0         | 2026-05-07 10:00:02+00
-- skos                | 0.98.0         | 2026-05-07 09:59:59+00

See Also