RDFJS compliance: the equals method

[pietercolpaert]

When using the toRDF method, the jsonld.js library does not return RDFJS spec compliant quads as the quads to not contain an equals() function as required by the spec.

Hotfixed this using the DataFactory class from the N3.js library as follows:

  addEqualsMethodToQuad (quad) {
    quad.equals = DataFactory.internal.Quad.prototype.equals;
    if (quad.subject.termType === 'NamedNode')
      quad.subject.equals = DataFactory.internal.NamedNode.prototype.equals;
    if (quad.subject.termType === 'BlankNode')
      quad.subject.equals = DataFactory.internal.BlankNode.prototype.equals;
    if (quad.predicate.termType === 'NamedNode')
      quad.predicate.equals = DataFactory.internal.NamedNode.prototype.equals;
    if (quad.predicate.termType === 'BlankNode')
      quad.predicate.equals = DataFactory.internal.BlankNode.prototype.equals;
    if (quad.object.termType === 'NamedNode')
      quad.object.equals = DataFactory.internal.NamedNode.prototype.equals;
    if (quad.object.termType === 'BlankNode')
      quad.object.equals = DataFactory.internal.BlankNode.prototype.equals;
    if (quad.object.termType === 'Literal')
      quad.object.equals = DataFactory.internal.Literal.prototype.equals;
    if (quad.graph.termType === 'NamedNode')
      quad.graph.equals = DataFactory.internal.NamedNode.prototype.equals;
    if (quad.graph.termType === 'BlankNode')
      quad.graph.equals = DataFactory.internal.BlankNode.prototype.equals;
    return quad;
  }

Fixing this into this library may allow for the N3.js library compatibility and the compatibility to the entire RDF-Ext family.

[RubenVerborgh]

The idea would actually be that parsers accept a factory argument, such that they can instantiate RDF.js objects of a particular library (like here).