defmodule RDF.Quad do
@moduledoc """
Helper functions for RDF quads.
An RDF Quad is represented as a plain Elixir tuple consisting of four valid
RDF values for subject, predicate, object and a graph name.
"""
alias RDF.{Statement, PropertyMap}
@type t :: {
Statement.subject(),
Statement.predicate(),
Statement.object(),
Statement.graph_name()
}
@type coercible ::
{
Statement.coercible_subject(),
Statement.coercible_predicate(),
Statement.coercible_object(),
Statement.coercible_graph_name()
}
@type mapping_value :: {String.t(), String.t(), any, String.t()}
# deprecated: This will be removed in v0.11.
@type t_values :: mapping_value
@doc """
Creates a `RDF.Quad` with proper RDF values.
An error is raised when the given elements are not coercible to RDF values.
Note: The `RDF.quad` function is a shortcut to this function.
## Examples
iex> RDF.Quad.new("http://example.com/S", "http://example.com/p", 42, "http://example.com/Graph")
{~I<http://example.com/S>, ~I<http://example.com/p>, RDF.literal(42), ~I<http://example.com/Graph>}
iex> RDF.Quad.new(EX.S, EX.p, 42, EX.Graph)
{RDF.iri("http://example.com/S"), RDF.iri("http://example.com/p"), RDF.literal(42), RDF.iri("http://example.com/Graph")}
iex> RDF.Quad.new(EX.S, :p, 42, EX.Graph, RDF.PropertyMap.new(p: EX.p))
{RDF.iri("http://example.com/S"), RDF.iri("http://example.com/p"), RDF.literal(42), RDF.iri("http://example.com/Graph")}
"""
@spec new(
Statement.coercible_subject(),
Statement.coercible_predicate(),
Statement.coercible_object(),
Statement.coercible_graph_name(),
PropertyMap.t() | nil
) :: t
def new(subject, predicate, object, graph_name, property_map \\ nil)
def new(subject, predicate, object, graph_name, nil) do
{
Statement.coerce_subject(subject),
Statement.coerce_predicate(predicate),
Statement.coerce_object(object),
Statement.coerce_graph_name(graph_name)
}
end
def new(subject, predicate, object, graph_name, %PropertyMap{} = property_map) do
{
Statement.coerce_subject(subject),
Statement.coerce_predicate(predicate, property_map),
Statement.coerce_object(object),
Statement.coerce_graph_name(graph_name)
}
end
@doc """
Creates a `RDF.Quad` with proper RDF values.
An error is raised when the given elements are not coercible to RDF values.
Note: The `RDF.quad` function is a shortcut to this function.
## Examples
iex> RDF.Quad.new {"http://example.com/S", "http://example.com/p", 42, "http://example.com/Graph"}
{~I<http://example.com/S>, ~I<http://example.com/p>, RDF.literal(42), ~I<http://example.com/Graph>}
iex> RDF.Quad.new {EX.S, EX.p, 42, EX.Graph}
{RDF.iri("http://example.com/S"), RDF.iri("http://example.com/p"), RDF.literal(42), RDF.iri("http://example.com/Graph")}
iex> RDF.Quad.new {EX.S, EX.p, 42}
{RDF.iri("http://example.com/S"), RDF.iri("http://example.com/p"), RDF.literal(42), nil}
iex> RDF.Quad.new {EX.S, :p, 42, EX.Graph}, RDF.PropertyMap.new(p: EX.p)
{RDF.iri("http://example.com/S"), RDF.iri("http://example.com/p"), RDF.literal(42), RDF.iri("http://example.com/Graph")}
"""
@spec new(Statement.coercible(), PropertyMap.t() | nil) :: t
def new(statement, property_map \\ nil)
def new({subject, predicate, object, graph_name}, property_map) do
new(subject, predicate, object, graph_name, property_map)
end
def new({subject, predicate, object}, property_map) do
new(subject, predicate, object, nil, property_map)
end
@doc """
Returns a tuple of native Elixir values from a `RDF.Quad` of RDF terms.
When a `:context` option is given with a `RDF.PropertyMap`, predicates will
be mapped to the terms defined in the `RDF.PropertyMap`, if present.
Returns `nil` if one of the components of the given tuple is not convertible via `RDF.Term.value/1`.
## Examples
iex> RDF.Quad.values {~I<http://example.com/S>, ~I<http://example.com/p>, RDF.literal(42), ~I<http://example.com/Graph>}
{"http://example.com/S", "http://example.com/p", 42, "http://example.com/Graph"}
iex> {~I<http://example.com/S>, ~I<http://example.com/p>, RDF.literal(42), ~I<http://example.com/Graph>}
...> |> RDF.Quad.values(context: %{p: ~I<http://example.com/p>})
{"http://example.com/S", :p, 42, "http://example.com/Graph"}
"""
@spec values(t, keyword) :: mapping_value | nil
def values(quad, opts \\ []) do
if property_map = PropertyMap.from_opts(opts) do
map(quad, Statement.default_property_mapping(property_map))
else
map(quad, &Statement.default_term_mapping/1)
end
end
@doc """
Returns a tuple where each element from a `RDF.Quad` is mapped with the given function.
Returns `nil` if one of the components of the given tuple is not convertible via `RDF.Term.value/1`.
The function `fun` will receive a tuple `{statement_position, rdf_term}` where
`statement_position` is one of the atoms `:subject`, `:predicate`, `:object` or
`:graph_name` while `rdf_term` is the RDF term to be mapped. When the given function
returns `nil` this will be interpreted as an error and will become the overhaul
result of the `map/2` call.
## Examples
iex> {~I<http://example.com/S>, ~I<http://example.com/p>, RDF.literal(42), ~I<http://example.com/Graph>}
...> |> RDF.Quad.map(fn
...> {:object, object} ->
...> RDF.Term.value(object)
...> {:graph_name, graph_name} ->
...> graph_name
...> {_, resource} ->
...> resource |> to_string() |> String.last() |> String.to_atom()
...> end)
{:S, :p, 42, ~I<http://example.com/Graph>}
"""
@spec map(t, Statement.term_mapping()) :: mapping_value | nil
def map({subject, predicate, object, graph_name}, fun) do
with subject_value when not is_nil(subject_value) <- fun.({:subject, subject}),
predicate_value when not is_nil(predicate_value) <- fun.({:predicate, predicate}),
object_value when not is_nil(object_value) <- fun.({:object, object}),
graph_name_value <- fun.({:graph_name, graph_name}) do
{subject_value, predicate_value, object_value, graph_name_value}
else
_ -> nil
end
end
@doc """
Checks if the given tuple is a valid RDF quad.
The elements of a valid RDF quad must be RDF terms. On the subject
position only IRIs and blank nodes allowed, while on the predicate and graph
name position only IRIs allowed. The object position can be any RDF term.
"""
@spec valid?(t | any) :: boolean
def valid?(tuple)
def valid?({_, _, _, _} = quad), do: Statement.valid?(quad)
def valid?(_), do: false
end
