Exploring Graphs with Elixir/

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Query the Local RDF Service: Major Query Forms

Query the Local RDF Service: Major Query Forms

Learn how to use the SELECT and CONSTRUCT query forms to query the local RDF service.

We'll cover the following...

Load the data

We’ll need some RDF data. To keep things simple, let’s take the RDF description for the book graph:

iex> graph_service RDFGraph
iex> graph_create read_graph("book.ttl")
iex> graph_info
Queries to load the book graph

Execute the commands above in the terminal below to load the book graph:

#---
# Excerpted from "Exploring Graphs with Elixir",
# published by The Pragmatic Bookshelf.
# Copyrights apply to this code. It may not be used to create training material,
# courses, books, articles, and the like. Contact us if you are in doubt.
# We make no guarantees that this code is fit for any purpose.
# Visit http://www.pragmaticprogrammer.com/titles/thgraphs for more book information.
#---
defmodule RDFGraph.Vocab do
  use RDF.Vocabulary.Namespace

  alias RDF.NS.XSD

  defvocab(DC,
    base_iri: "http://purl.org/dc/elements/1.1/",
    file: "dc.ttl"
    # terms: ~w[
    #   contributor coverage creator date description format
    #   identifier language publisher relation rights source
    #   subject title type
    # ]
  )

  defvocab(BIBO,
    base_iri: "http://purl.org/ontology/bibo/",
    file: "bibo.ttl",
    case_violations: :ignore
  )

  defvocab(DCTERMS,
    base_iri: "http://purl.org/dc/terms/",
    file: "bibo.ttl",
    case_violations: :ignore
  )

  defvocab(EVENT,
    base_iri: "http://purl.org/NET/c4dm/event.owl#",
    file: "bibo.ttl"
  )

  defvocab(FOAF,
    base_iri: "http://xmlns.com/foaf/0.1/",
    file: "bibo.ttl"
  )

  defvocab(PRISM,
    base_iri: "http://prismstandard.org/namespaces/1.2/basic/",
    file: "bibo.ttl"
  )

  defvocab(SCHEMA,
    base_iri: "http://schemas.talis.com/2005/address/schema#",
    file: "bibo.ttl"
  )

  defvocab(STATUS,
    base_iri: "http://purl.org/ontology/bibo/status/",
    file: "bibo.ttl",
    case_violations: :ignore
  )

  ## book function defintions

  def book() do

    import RDF.Sigils
    alias RDF.NS.{XSD}

    ~I<urn:isbn:978-1-68050-252-7>
    |> RDF.type(BIBO.Book)
    |> DC.creator(
      ~I<https://twitter.com/bgmarx>
    )
    |> DC.date("2018-03-14")
    |> DC.format(~L"Paper")
    |> DC.identifier(~L"adopting_elixir")
    |> DC.identifier(RDF.literal("urn:isbn:978-1-68050-252-7",
        datatype: XSD.anyURI()))
    |> DC.publisher(~I<https://pragprog.com/>)
    |> DC.title(~L"Adopting Elixir"en)
  end

  def book_long() do

    alias RDF.NS.{XSD}

    s = RDF.iri("urn:isbn:978-1-68050-252-7")

    t0 = {s, RDF.type(), RDF.iri(BIBO.Book)}
    t1 = {s, DC.creator(), RDF.iri("https://twitter.com/bgmarx")}
    t2 = {s, DC.creator(), RDF.iri("https://twitter.com/josevalim")}
    t3 = {s, DC.creator(), RDF.iri("https://twitter.com/redrapids")}
    t4 = {s, DC.date(), RDF.literal("2018-03-14", datatype: XSD.date())}
    t5 = {s, DC.format(), RDF.literal("Paper")}
    t6 = {s, DC.identifier(), RDF.literal("adopting_elixir")}
    t7 = {s, DC.identifier(), RDF.literal("urn:isbn:978-1-68050-252-7", datatype: XSD.anyURI())}
    t8 = {s, DC.publisher(), RDF.iri("https://pragprog.com/")}
    t9 = {s, DC.title(), RDF.literal("Adopting Elixir", language: "en")}

    RDF.Description.new([t0, t1, t2, t3, t4, t5, t6, t7, t8, t9])
  end

end
Load the book graph

SELECT

Let’s have a look at the SELECT query ...