rdf-ex/lib/rdf/triple.ex
2016-11-04 22:13:06 +01:00

75 lines
2.4 KiB
Elixir

defmodule RDF.Triple do
@moduledoc """
Defines a RDF Triple.
A Triple is a plain Elixir tuple consisting of three valid RDF values for
subject, predicate and object.
"""
alias RDF.{BlankNode, Literal}
@type subject :: URI.t | BlankNode.t
@type predicate :: URI.t
@type object :: URI.t | BlankNode.t | Literal.t
@type convertible_subject :: subject | atom | String.t
@type convertible_predicate :: predicate | atom | String.t
@type convertible_object :: object | atom | String.t # TODO: all basic Elixir types convertible to Literals
@doc """
Creates a `RDF.Triple` with proper RDF values.
An error is raised when the given elements are not convertible to RDF values.
Note: The `RDF.triple` function is a shortcut to this function.
# Examples
iex> RDF.Triple.new("http://example.com/S", "http://example.com/p", 42)
{RDF.uri("http://example.com/S"), RDF.uri("http://example.com/p"), RDF.literal(42)}
"""
def new(subject, predicate, object) do
{
convert_subject(subject),
convert_predicate(predicate),
convert_object(object)
}
end
@doc """
Creates a `RDF.Triple` with proper RDF values.
An error is raised when the given elements are not convertible to RDF values.
Note: The `RDF.triple` function is a shortcut to this function.
# Examples
iex> RDF.Triple.new {"http://example.com/S", "http://example.com/p", 42}
{RDF.uri("http://example.com/S"), RDF.uri("http://example.com/p"), RDF.literal(42)}
"""
def new({subject, predicate, object}), do: new(subject, predicate, object)
@doc false
def convert_subject(uri)
def convert_subject(uri = %URI{}), do: uri
def convert_subject(bnode = %BlankNode{}), do: bnode
def convert_subject(uri) when is_atom(uri) or is_binary(uri), do: RDF.uri(uri)
def convert_subject(arg), do: raise RDF.Triple.InvalidSubjectError, subject: arg
@doc false
def convert_predicate(uri)
def convert_predicate(uri = %URI{}), do: uri
def convert_predicate(uri) when is_atom(uri) or is_binary(uri), do: RDF.uri(uri)
def convert_predicate(arg), do: raise RDF.Triple.InvalidPredicateError, predicate: arg
@doc false
def convert_object(uri)
def convert_object(uri = %URI{}), do: uri
def convert_object(literal = %Literal{}), do: literal
def convert_object(bnode = %BlankNode{}), do: bnode
def convert_object(atom) when is_atom(atom), do: RDF.uri(atom)
def convert_object(arg), do: Literal.new(arg)
end