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Getting Started with roxigraph

Introduction

roxigraph provides RDF storage and SPARQL query capabilities for R by wrapping the Oxigraph graph database. This vignette introduces the core functionality.

Creating an RDF Store

library(roxigraph)

# Create an in-memory store
store <- rdf_store()

For persistent storage that survives R sessions:

store <- rdf_store("/path/to/database")

Loading RDF Data

roxigraph supports multiple RDF serialization formats:

Turtle

turtle_data <- '
@prefix foaf: <http://xmlns.com/foaf/0.1/> .
@prefix ex: <http://example.org/> .

ex:alice a foaf:Person ;
         foaf:name "Alice" ;
         foaf:age 30 ;
         foaf:knows ex:bob .

ex:bob a foaf:Person ;
       foaf:name "Bob" ;
       foaf:age 25 .
'

rdf_load(store, turtle_data, format = "turtle")
rdf_size(store)
#> [1] 7

N-Triples

store2 <- rdf_store()
nt_data <- '<http://example.org/s> <http://example.org/p> "object" .'
rdf_load(store2, nt_data, format = "ntriples")

From Files

rdf_load_file(store, "data.ttl", format = "turtle")
rdf_load_file(store, "data.nt") # Format guessed from extension

SPARQL Queries

SELECT Queries

# Find all people and their names
results <- sparql_query(store, "
  PREFIX foaf: <http://xmlns.com/foaf/0.1/>
  SELECT ?person ?name
  WHERE {
    ?person a foaf:Person ;
            foaf:name ?name .
  }
")
results
#>                       person    name
#> 1   <http://example.org/bob>   "Bob"
#> 2 <http://example.org/alice> "Alice"

Filtering and Sorting

# Find people over 26
sparql_query(store, "
  PREFIX foaf: <http://xmlns.com/foaf/0.1/>
  SELECT ?name ?age
  WHERE {
    ?person foaf:name ?name ;
            foaf:age ?age .
    FILTER(?age > 26)
  }
  ORDER BY DESC(?age)
")
#>      name                                              age
#> 1 "Alice" "30"^^<http://www.w3.org/2001/XMLSchema#integer>

ASK Queries

# Check if Alice exists
sparql_query(store, "
  PREFIX ex: <http://example.org/>
  ASK { ex:alice ?p ?o }
")
#> [1] TRUE

Aggregation

sparql_query(store, "
  PREFIX foaf: <http://xmlns.com/foaf/0.1/>
  SELECT (COUNT(?person) as ?count) (AVG(?age) as ?avg_age)
  WHERE {
    ?person a foaf:Person ;
            foaf:age ?age .
  }
")
#>                                             count
#> 1 "2"^^<http://www.w3.org/2001/XMLSchema#integer>
#>                                              avg_age
#> 1 "27.5"^^<http://www.w3.org/2001/XMLSchema#decimal>

Modifying Data

SPARQL Update

# Add new data
sparql_update(store, "
  PREFIX foaf: <http://xmlns.com/foaf/0.1/>
  PREFIX ex: <http://example.org/>

  INSERT DATA {
    ex:carol a foaf:Person ;
             foaf:name 'Carol' ;
             foaf:age 28 .
  }
")

rdf_size(store)
#> [1] 10

Direct Triple Manipulation

# Add a triple
rdf_add(
    store, "<http://example.org/carol>",
    "<http://xmlns.com/foaf/0.1/knows>",
    "<http://example.org/alice>"
)

# Remove a triple
rdf_remove(
    store, "<http://example.org/carol>",
    "<http://xmlns.com/foaf/0.1/knows>",
    "<http://example.org/alice>"
)

Serialization

Export your RDF data:

# Export to N-Quads format
output <- rdf_serialize(store, format = "nquads")
cat(substr(output, 1, 500), "...\n")
#> <http://example.org/carol> <http://xmlns.com/foaf/0.1/age> "28"^^<http://www.w3.org/2001/XMLSchema#integer> .
#> <http://example.org/carol> <http://xmlns.com/foaf/0.1/name> "Carol" .
#> <http://example.org/carol> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://xmlns.com/foaf/0.1/Person> .
#> <http://example.org/bob> <http://xmlns.com/foaf/0.1/age> "25"^^<http://www.w3.org/2001/XMLSchema#integer> .
#> <http://example.org/bob> <http://xmlns.com/foaf/0.1/name> "Bob" .
#> <http://example.org/bob> <http:/ ...

Supported output formats: nquads, trig, rdfxml

Best Practices

  1. Use prefixes in SPARQL queries for readability
  2. Choose the right storage: In-memory for temporary data, persistent for large datasets
  3. Batch operations: Use rdf_load() for bulk data rather than individual rdf_add() calls
  4. Close persistent stores: R will handle cleanup, but explicit management helps with large databases

Further Reading

These binaries (installable software) and packages are in development.
They may not be fully stable and should be used with caution. We make no claims about them.
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