How to use sparql-engine - 6 common examples

@prefix :  .
  :a foaf:name "a" .
  :b foaf:name "b" .
`).forEach(t => {
  graph._store.addTriple(t)
})

const query = `
  PREFIX foaf: 
  SELECT ?name
  WHERE {
    ?s foaf:name ?name .
  }`

// Creates a plan builder for the RDF dataset
const builder = new PlanBuilder(dataset)

// Get an iterator to evaluate the query
const iterator = builder.build(query)

// Read results
iterator.subscribe(bindings => {
  console.log('Find solutions:', bindings.toObject())
}, err => {
  console.error('error', err)
}, () => {
  console.log('Query evaluation complete!')
})

db.put([triple1, triple2], () => {
  const graph = new LevelRDFGraph(db)
  const dataset = new HashMapDataset('http://example.org#default', graph)

  const query = `
    PREFIX foaf: 
    SELECT ?name
    WHERE {
      ?s foaf:name ?name .
    }`

  // Creates a plan builder for the RDF dataset
  const builder = new PlanBuilder(dataset)

  // Get an iterator to evaluate the query
  const iterator = builder.build(query)

  // Read results
  iterator.subscribe(bindings => {
    console.log('Find solutions:', bindings.toObject())
  }, err => {
    console.error('error', err)
  }, () => {
    console.log('Query evaluation complete!')
  })
})

db.put([triple1, triple2], () => {
  const graph = new LevelRDFGraph(db)
  const dataset = new HashMapDataset('http://example.org#default', graph)

  const query = `
    PREFIX foaf: 
    SELECT ?name
    WHERE {
      ?s foaf:name ?name .
    }`

  // Creates a plan builder for the RDF dataset
  const builder = new PlanBuilder(dataset)

  // Get an iterator to evaluate the query
  const iterator = builder.build(query)

  // Read results
  iterator.subscribe(bindings => {

})
  }

  find (triple) {
    const { subject, predicate, object } = formatTriplePattern(triple)
    return this._store.getTriples(subject, predicate, object)
  }

  estimateCardinality (triple) {
    const { subject, predicate, object } = formatTriplePattern(triple)
    return Promise.resolve(this._store.countTriples(subject, predicate, object))
  }
}

const graph = new N3Graph()
const dataset = new HashMapDataset('http://example.org#default', graph)

// Load some RDF data into the graph
const parser = new Parser()
parser.parse(`
  @prefix foaf:  .
  @prefix :  .
  :a foaf:name "a" .
  :b foaf:name "b" .
`).forEach(t => {
  graph._store.addTriple(t)
})

const query = `
  PREFIX foaf: 
  SELECT ?name
  WHERE {

evalBGP (bgp) {
    // Connect the Node.js Readable stream
    // into the SPARQL query engine using the fromAsync method
    return Pipeline.getInstance().fromAsync(input => {
      // rewrite variables using levelgraph API
      bgp = bgp.map(t => {
        if (t.subject.startsWith('?')) {
          t.subject = this._db.v(t.subject.substring(1))
        }
        if (t.predicate.startsWith('?')) {
          t.predicate = this._db.v(t.predicate.substring(1))
        }
        if (t.object.startsWith('?')) {
          t.object = this._db.v(t.object.substring(1))
        }
        return t
      })
      // Evaluates the BGP using Levelgraph stream API
      const stream = this._db.searchStream(bgp)

      stream.on('data', results => input.next(BindingBase.fromObject(results)))
    })