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rdf-parser-abstract

Abstract base class for RDF-Interfaces parser implementations.

Usage

The AbstractParser class adds default implementations for .parse(data, callback, base, filter, graph) and .stream(inputStream, base, filter). Only the .process(data, callback, base, filter, done) method must be implemented.

Your own parser hast to inherit from the abstract parser. First let's install the package. Start a terminal and run:

npm install rdf-abstract-parser --save

Now let's start coding. To inherit from the abstract parser, we have to load the inherits and the AbstractParser itself first:

var inherits = require('inherits')
var AbstractParser = require('rdf-abstract-parser')

Your parser must accept the optional parameter rdf to use the given RDF environment. To initialize the AbstractParser, you have to call the AbstractParser constructor in your own constructor.

function YourParser (options) {
  // use the given RDF environment or RDF-Ext if none was given
  this.rdf = options.rdf || require('rdf-ext')

// call the AbstractParser constructor
  AbstractParser.call(this, rdf)
}

After the constructor code you have to inherit with the inherits function.

inherits(YourParser, AbstractParser)

Only the .process method is required to be implemented. The base parameter is optional, let's check if it is given and createt a NamedNode from the string, so we can use it for the graph property for the quads. The filter parameter is optional, so let's assign a accept all triples filter, if none was given. Finally you can implement your parser code. The example code accepts strings with one triple per line and spo space separated and only named node without additional escaping. To parse the string we only have to split the string per line and than split every line into spo. For every spo we create a quad with the RDF environment and check if the filter accepts the quad. If the filter accepts the quad we can forward it. That's it, your parser is complete!

YourParser.prototype.process = function (data, callback, base, filter, done) {
  var self = this

// create a NamedNode if the base parameter is given
base = !!base ? null : self.rdf.createNamedNode(base.toString())

  // use a accept all triples filter, if none was given
  filter = filter || function () {
    return true
  }

  // split string into triples
  data.split('\n').forEach(function (line) {
    // split triple into spo
    var spo = line.split(' ')

    // create the Quad using the RDF environment
    var quad = self.rdf.createQuad(
      self.rdf.createNamedNode(spo[0]),
      self.rdf.createNamedNode(spo[1]),
      self.rdf.createNamedNode(spo[2]),
      base)

  // only forward the quad if the filter accepts it
    if (filter(quad)) {
      // forward the quad
  	callback(quad)
  }
  })
}