rdflib 0.1.3

A pure Dart package for working with RDF (resource description framework).

RDFLib

A pure Dart package for working with RDF (resource description framework).

Features

• Create triple instances (with data types)
• Create a graph to store triples without duplicates
• Find triples based on criteria
• Export graph to turtle ttl format (default)
• Bind long namespace with customized shortened name for readability
• Include reserved vocabulary of OWL 2
• Parse local turtle ttl file and store triples in the graph in memory

Getting started

Refer to the code example below, or go to /example to find out more!

For testing the rdflib package

# create a dart project for testing
dart create test_rdflib
cd test_rdflib
# install rdflib as the dependency with dart pub add
dart pub add rdflib
# copy the following code to /bin/test_rdflib.dart
# run the file with dart
dart run

Usage

Head over to our GitHub repo to check out more examples!

1. General usage

The following code snippet shows how to:

1. Create a Graph instance;
2. Create and store triples with different data types;
3. Find entities based on customized criteria;
4. Bind shorted string to long namespace;
5. Export graph data to turtle file;

import 'dart:io';
import 'package:rdflib/rdflib.dart';

main() async {
  Graph g = Graph();

  URIRef example = URIRef.fullUri('http://example.org');

  // subject and predicate should be a valid URIRef instance
  URIRef donna = example.slash('donna');

  g.add(Triple(sub: donna, pre: RDF.type, obj: FOAF.Person));

  // add duplicated record
  g.add(Triple(sub: donna, pre: RDF.type, obj: FOAF.Person));
  g.add(Triple(sub: donna, pre: FOAF.nick, obj: Literal('donna', lang: 'en')));
  g.add(Triple(sub: donna, pre: FOAF.name, obj: Literal('Donna Fales')));

  // add duplicated record
  g.add(Triple(sub: donna, pre: FOAF.name, obj: Literal('Donna Fales')));
  g.add(Triple(
      sub: donna,
      pre: FOAF.mbox,
      obj: URIRef.fullUri('mailto:[e-mail]')));

  // add another in the graph
  URIRef ed = example.slash('edward');
  g.add(Triple(sub: ed, pre: RDF.type, obj: FOAF.Person));
  g.add(Triple(
      sub: ed, pre: FOAF.nick, obj: Literal('ed', datatype: XSD.string)));
  g.add(Triple(sub: ed, pre: FOAF.name, obj: 'Edward Scissorhands'));
  g.add(Triple(
      sub: ed,
      pre: FOAF.mbox,
      obj: Literal('[e-mail]', datatype: XSD.anyURI)));

  // TEST triples should print correctly
  print('-' * 30);
  for (Triple t in g.triples) {
    // duplicated records will not be added and printed out
    print(t);
  }

  print('-' * 30);

  // TEST correct subjects/objects should print out
  for (URIRef s in g.subjects(RDF.type, FOAF.Person)) {
    for (var o in g.objects(s, FOAF.mbox)) {
      // should print out URIRef(mailto:[e-mail]) and
      // Literal([e-mail], datatype: URIRef(http://www.w3.org/2001/XMLSchema#anyURI))
      print(o);
    }
  }

  // bind 'foaf' to FOAF for easy readout
  g.bind('foaf', FOAF(ns: FOAF.foaf));

  /// uncomment the following line to test binding a customized namespace
  /// g.bind('example', Namespace(ns: 'http://example.org/'));

  // export graph to turtle format, create directory if it doesn't exist
  String currentPath = Directory.current.path;
  String examplePath = '$currentPath/example';
  if (!await Directory(examplePath).exists()) {
    await Directory(examplePath).create(recursive: true);
  }
  g.serialize(format: 'ttl', dest: '$examplePath/ex1.ttl');
}

2. SOLID Health Ontology Example

import '../lib/rdflib.dart';

main() {
  Graph g = Graph();

  Namespace shData = Namespace(ns: 'http://silo.net.au/data/SOLID-Health#');
  Namespace shOnto =
  Namespace(ns: 'http://sii.cecs.anu.edu.au/onto/SOLID-Health#');

  URIRef newAssessTab = shData.withAttr('AssessmentTab-p43623-20220727T120913');
  g.addNamedIndividual(newAssessTab);

  // Literal string
  g.add(Triple(
      sub: newAssessTab, pre: RDF.type, obj: shOnto.withAttr('AssessmentTab')));

  // Literal string
  g.add(Triple(
      sub: newAssessTab,
      pre: shOnto.withAttr('asthmaControl'),
      obj: Literal('Poor Control')));

  // Literal integer
  g.add(Triple(
      sub: newAssessTab,
      pre: shOnto.withAttr('diastolicBloodPressure'),
      obj: Literal('75')));

  // Literal float/double
  g.add(Triple(
      sub: newAssessTab,
      pre: shOnto.withAttr('systolicBloodPressure'),
      obj: Literal('125.0')));

  URIRef newSeeAndDoTab = shData.withAttr('SeeAndDoTab-p43623-20220727T120913');
  URIRef newSeeAndDoOption =
  shData.withAttr('SeeAndDoOption-p43623-20220727T120913-fitnessDrive');

  g.addNamedIndividual(newSeeAndDoTab);
  g.addNamedIndividual(newSeeAndDoOption);
  // link two triple individuals
  g.addObjectProperty(
      newSeeAndDoTab, shOnto.withAttr('hasSeeAndDoOption'), newSeeAndDoOption);

  /// binding for readability
  g.bind('sh-data', shData);
  g.bind('sh-onto', shOnto);

  g.serialize(dest: 'example/ex2.ttl');
}

3. Parsing local turtle file

import 'package:rdflib/rdflib.dart';

main() async {
  String filePath = 'example/ex1.ttl';
  // create a graph to read turtle file and store info
  Graph g = Graph();
  await g.parse(filePath);
  // full format of triples (will use shorthand in serialization/export)
  for (Triple t in g.triples) {
    print(t);
  }
  // export it to a new file (should equivalent to the original one)
  g.serialize(format: 'ttl', dest: 'example/ex3.ttl');
}

Additional information

Useful resources

1. RDFLib
2. Introduction to RDF

How to contribute

Make a pull request on our GitHub repo!

Acknowledgement

This rdflib dart package is modelled on the RDFLib.