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Export a Knowledge Graph to RDF 1.1 Turtle

Source: R/causal_kg_io.R
causal_kg_to_turtle.Rd

Serialises an edaphos_causal_kg as RDF 1.1 Turtle (https://www.w3.org/TR/turtle/), the W3C's canonical human-readable triple language. Each edge becomes a reified rdf:Statement so confidence, evidence, source and timestamp are preserved losslessly; each node is given a stable IRI inside a user-controlled namespace. The emitter is written in pure R with no external dependency — the output is guaranteed parseable by any RDF 1.1-conformant consumer (rdflib, Jena, Virtuoso, Blazegraph, GraphDB, Oxigraph …).

Usage

causal_kg_to_turtle(
  kg,
  path = NULL,
  base_uri = "https://edaphos.io/kg/",
  schema_uri = "https://edaphos.io/schema#",
  namespaces = character(0),
  include_metadata = TRUE
)

Arguments

kg

An edaphos_causal_kg.

path

Optional output file path. When NULL (default), the Turtle document is returned as a single character string.

base_uri

Character — base IRI for the KG. Must end with "/" or "#". Default "https://edaphos.io/kg/".

schema_uri

Character — IRI of the eds: schema namespace. Default "https://edaphos.io/schema#".

namespaces

Named character vector of extra prefix bindings to declare. Useful when you want to reference external vocabularies (e.g. c(agrovoc = "http://aims.fao.org/aos/agrovoc/")).

include_metadata

Logical — emit document-level metadata (creation time, edaphos version) as prov: statements. Default TRUE.

Value

When path is NULL, invisibly returns the Turtle document as a length-1 character vector. When path is given, writes the document to disk and invisibly returns path.

Details

The emitted graph uses the following prefixes by default (all overridable via namespaces):

  • ed: — edaphos KG namespace (one IRI per node and edge).

  • eds: — edaphos schema namespace (defines eds:Causes, eds:confidence, eds:evidence, eds:source).

  • rdf:, rdfs:, xsd:, prov:, dct: — standard W3C vocabularies.

Every node L becomes an IRI <base_uri>node/<sanitised_L>; every edge becomes an IRI <base_uri>edge/<cause>__<effect> typed as rdf:Statement, with rdf:subject / rdf:predicate / rdf:object pointing at the nodes and eds:Causes used as the predicate for the causal direction. Provenance is attached via dct:source (bibliographic identifier) and prov:generatedAtTime (timestamp).

References

Beckett, D. (2014). RDF 1.1 Turtle — Terse RDF Triple Language. W3C Recommendation.

See also

causal_kg_save() for binary RDS persistence.

Examples

# \donttest{
  kg <- causal_kg_new()
  kg <- causal_kg_add_edge(kg, "precipitation", "soc",
                            source = "Jenny 1941",
                            evidence = "Higher precipitation favours SOC.",
                            confidence = 0.9)
  ttl <- causal_kg_to_turtle(kg)
  substr(ttl, 1, 200)
#> [1] "@prefix ed: <https://edaphos.io/kg/node/> .\n@prefix edge: <https://edaphos.io/kg/edge/> .\n@prefix eds: <https://edaphos.io/schema#> .\n@prefix rdf:  <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .\n@pre"

  # Write to disk and (optionally) round-trip through rdflib if
  # installed -- a useful SPARQL-queryable artefact.
  tf <- tempfile(fileext = ".ttl")
  causal_kg_to_turtle(kg, tf)
# }