506 lines
18 KiB
Elixir
506 lines
18 KiB
Elixir
defmodule RDF.Description do
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@moduledoc """
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Defines a RDF Description.
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A `RDF.Description` represents a set of `RDF.Triple`s about a subject.
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"""
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defstruct subject: nil, predications: %{}
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@behaviour Access
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import RDF.Statement
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@type t :: module
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@doc """
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Creates a new `RDF.Description` about the given subject.
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When given a triple, it must contain the subject.
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When given a list of statements, the first one must contain a subject.
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"""
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@spec new(RDF.Statement.convertible_subject) :: RDF.Description.t
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def new(subject)
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def new({subject, predicate, object}),
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do: new(subject) |> add(predicate, object)
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def new([statement | more_statements]),
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do: new(statement) |> add(more_statements)
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def new(subject),
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do: %RDF.Description{subject: convert_subject(subject)}
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def new(%RDF.Description{} = description, predicate, objects),
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do: RDF.Description.add(description, predicate, objects)
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def new(subject, predicate, objects),
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do: new(subject) |> add(predicate, objects)
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def new(subject, statements) when is_list(statements),
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do: new(subject) |> add(statements)
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def new(subject, %RDF.Description{predications: predications}),
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do: %RDF.Description{new(subject) | predications: predications}
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def new(subject, predications = %{}),
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do: new(subject) |> add(predications)
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@doc """
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Add objects to a predicate of a `RDF.Description`.
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# Examples
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iex> RDF.Description.add(RDF.Description.new({EX.S, EX.P1, EX.O1}), EX.P2, EX.O2)
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RDF.Description.new([{EX.S, EX.P1, EX.O1}, {EX.S, EX.P2, EX.O2}])
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iex> RDF.Description.add(RDF.Description.new({EX.S, EX.P, EX.O1}), EX.P, [EX.O2, EX.O3])
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RDF.Description.new([{EX.S, EX.P, EX.O1}, {EX.S, EX.P, EX.O2}, {EX.S, EX.P, EX.O3}])
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"""
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def add(description, predicate, objects)
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def add(description, predicate, objects) when is_list(objects) do
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Enum.reduce objects, description, fn (object, description) ->
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add(description, predicate, object)
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end
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end
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def add(%RDF.Description{subject: subject, predications: predications}, predicate, object) do
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with triple_predicate = convert_predicate(predicate),
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triple_object = convert_object(object),
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new_predications = Map.update(predications,
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triple_predicate, %{triple_object => nil}, fn objects ->
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Map.put_new(objects, triple_object, nil)
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end) do
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%RDF.Description{subject: subject, predications: new_predications}
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end
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end
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@doc """
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Adds statements to a `RDF.Description`.
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"""
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def add(description, statements)
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def add(description, {predicate, object}),
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do: add(description, predicate, object)
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def add(description = %RDF.Description{}, {subject, predicate, object}) do
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if convert_subject(subject) == description.subject,
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do: add(description, predicate, object),
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else: description
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end
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def add(description, statements) when is_list(statements) do
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Enum.reduce statements, description, fn (statement, description) ->
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add(description, statement)
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end
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end
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def add(%RDF.Description{subject: subject, predications: predications},
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%RDF.Description{predications: other_predications}) do
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merged_predications = Map.merge predications, other_predications,
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fn (_, objects, other_objects) -> Map.merge(objects, other_objects) end
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%RDF.Description{subject: subject, predications: merged_predications}
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end
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def add(description = %RDF.Description{}, predications = %{}) do
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Enum.reduce predications, description, fn ({predicate, objects}, description) ->
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add(description, predicate, objects)
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end
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end
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@doc """
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Puts objects to a predicate of a `RDF.Description`, overwriting all existing objects.
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# Examples
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iex> RDF.Description.put(RDF.Description.new({EX.S, EX.P, EX.O1}), EX.P, EX.O2)
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RDF.Description.new([{EX.S, EX.P, EX.O2}])
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iex> RDF.Description.put(RDF.Description.new({EX.S, EX.P1, EX.O1}), EX.P2, EX.O2)
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RDF.Description.new([{EX.S, EX.P1, EX.O1}, {EX.S, EX.P2, EX.O2}])
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"""
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def put(description, predicate, objects)
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def put(%RDF.Description{subject: subject, predications: predications},
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predicate, objects) when is_list(objects) do
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with triple_predicate = convert_predicate(predicate),
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triple_objects = Enum.reduce(objects, %{}, fn (object, acc) ->
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Map.put_new(acc, convert_object(object), nil) end),
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do: %RDF.Description{subject: subject,
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predications: Map.put(predications, triple_predicate, triple_objects)}
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end
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def put(desc = %RDF.Description{}, predicate, object),
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do: put(desc, predicate, [object])
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@doc """
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Adds statements to a `RDF.Description` and overwrites all existing statements with already used predicates.
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# Examples
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iex> RDF.Description.put(RDF.Description.new({EX.S, EX.P, EX.O1}), {EX.P, EX.O2})
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RDF.Description.new([{EX.S, EX.P, EX.O2}])
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iex> RDF.Description.new({EX.S, EX.P1, EX.O1}) |>
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...> RDF.Description.put([{EX.P2, EX.O2}, {EX.S, EX.P2, EX.O3}, {EX.P1, EX.O4}])
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RDF.Description.new([{EX.S, EX.P1, EX.O4}, {EX.S, EX.P2, EX.O2}, {EX.S, EX.P2, EX.O3}])
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iex> RDF.Description.new({EX.S, EX.P, EX.O1}) |>
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...> RDF.Description.put(RDF.Description.new(EX.S, EX.P, [EX.O1, EX.O2]))
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RDF.Description.new([{EX.S, EX.P, EX.O1}, {EX.S, EX.P, EX.O2}])
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iex> RDF.Description.new([{EX.S, EX.P1, EX.O1}, {EX.S, EX.P2, EX.O2}]) |>
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...> RDF.Description.put(%{EX.P2 => [EX.O3, EX.O4]})
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RDF.Description.new([{EX.S, EX.P1, EX.O1}, {EX.S, EX.P2, EX.O3}, {EX.S, EX.P2, EX.O4}])
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"""
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def put(description, statements)
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def put(desc = %RDF.Description{}, {predicate, object}),
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do: put(desc, predicate, object)
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def put(desc = %RDF.Description{}, {subject, predicate, object}) do
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if convert_subject(subject) == desc.subject,
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do: put(desc, predicate, object),
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else: desc
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end
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def put(desc = %RDF.Description{subject: subject}, statements) when is_list(statements) do
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statements
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|> Stream.map(fn
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{p, o} -> {convert_predicate(p), o}
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{^subject, p, o} -> {convert_predicate(p), o}
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{s, p, o} ->
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if convert_subject(s) == subject,
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do: {convert_predicate(p), o}
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bad -> raise ArgumentError, "#{inspect bad} is not a valid statement"
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end)
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|> Stream.filter(&(&1)) # filter nil values
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|> Enum.group_by(&(elem(&1, 0)), &(elem(&1, 1)))
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|> Enum.reduce(desc, fn ({predicate, objects}, desc) ->
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put(desc, predicate, objects) end)
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end
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def put(%RDF.Description{subject: subject, predications: predications},
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%RDF.Description{predications: other_predications}) do
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merged_predications = Map.merge predications, other_predications,
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fn (_, _, other_objects) -> other_objects end
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%RDF.Description{subject: subject, predications: merged_predications}
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end
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def put(description = %RDF.Description{}, predications = %{}) do
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Enum.reduce predications, description, fn ({predicate, objects}, description) ->
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put(description, predicate, objects)
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end
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end
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@doc """
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Deletes statements from a `RDF.Description`.
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"""
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def delete(description, predicate, objects)
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def delete(description, predicate, objects) when is_list(objects) do
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Enum.reduce objects, description, fn (object, description) ->
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delete(description, predicate, object)
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end
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end
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def delete(%RDF.Description{subject: subject, predications: predications} = descr, predicate, object) do
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with triple_predicate = convert_predicate(predicate),
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triple_object = convert_object(object) do
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if (objects = predications[triple_predicate]) && Map.has_key?(objects, triple_object) do
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%RDF.Description{
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subject: subject,
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predications:
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if map_size(objects) == 1 do
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Map.delete(predications, triple_predicate)
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else
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Map.update!(predications, triple_predicate, fn objects ->
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Map.delete(objects, triple_object)
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end)
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end
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}
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else
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descr
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end
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end
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end
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@doc """
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Deletes statements from a `RDF.Description`.
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"""
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def delete(description, statements)
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def delete(desc = %RDF.Description{}, {predicate, object}),
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do: delete(desc, predicate, object)
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def delete(description = %RDF.Description{}, {subject, predicate, object}) do
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if convert_subject(subject) == description.subject,
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do: delete(description, predicate, object),
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else: description
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end
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def delete(description, statements) when is_list(statements) do
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Enum.reduce statements, description, fn (statement, description) ->
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delete(description, statement)
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end
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end
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def delete(description = %RDF.Description{}, predications = %{}) do
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Enum.reduce predications, description, fn ({predicate, objects}, description) ->
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delete(description, predicate, objects)
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end
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end
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@doc """
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Fetches the objects for the given predicate of a Description.
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When the predicate can not be found `:error` is returned.
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# Examples
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iex> RDF.Description.fetch(RDF.Description.new({EX.S, EX.p, EX.O}), EX.p)
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{:ok, [RDF.uri(EX.O)]}
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iex> RDF.Description.fetch(RDF.Description.new([{EX.S, EX.P, EX.O1},
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...> {EX.S, EX.P, EX.O2}]), EX.P)
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{:ok, [RDF.uri(EX.O1), RDF.uri(EX.O2)]}
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iex> RDF.Description.fetch(RDF.Description.new(EX.S), EX.foo)
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:error
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"""
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def fetch(%RDF.Description{predications: predications}, predicate) do
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with {:ok, objects} <- Access.fetch(predications, convert_predicate(predicate)) do
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{:ok, Map.keys(objects)}
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end
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end
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@doc """
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Gets the objects for the given predicate of a Description.
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When the predicate can not be found the optionally given default value or `nil` is returned.
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# Examples
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iex> RDF.Description.get(RDF.Description.new({EX.S, EX.P, EX.O}), EX.P)
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[RDF.uri(EX.O)]
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iex> RDF.Description.get(RDF.Description.new(EX.S), EX.foo)
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nil
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iex> RDF.Description.get(RDF.Description.new(EX.S), EX.foo, :bar)
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:bar
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"""
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def get(description = %RDF.Description{}, predicate, default \\ nil) do
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case fetch(description, predicate) do
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{:ok, value} -> value
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:error -> default
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end
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end
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@doc """
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Gets and updates the objects of the given predicate of a Description, in a single pass.
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Invokes the passed function on the objects of the given predicate; this
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function should return either `{objects_to_return, new_object}` or `:pop`.
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If the passed function returns `{objects_to_return, new_objects}`, the return
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value of `get_and_update` is `{objects_to_return, new_description}` where
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`new_description` is the input `Description` updated with `new_objects` for
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the given predicate.
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If the passed function returns `:pop` the objects for the given predicate are
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removed and a `{removed_objects, new_description}` tuple gets returned.
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# Examples
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iex> RDF.Description.new({EX.S, EX.P, EX.O}) |>
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...> RDF.Description.get_and_update(EX.P, fn current_objects ->
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...> {current_objects, EX.NEW}
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...> end)
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{[RDF.uri(EX.O)], RDF.Description.new({EX.S, EX.P, EX.NEW})}
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iex> RDF.Description.new([{EX.S, EX.P1, EX.O1}, {EX.S, EX.P2, EX.O2}]) |>
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...> RDF.Description.get_and_update(EX.P1, fn _ -> :pop end)
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{[RDF.uri(EX.O1)], RDF.Description.new({EX.S, EX.P2, EX.O2})}
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"""
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def get_and_update(description = %RDF.Description{}, predicate, fun) do
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with triple_predicate = convert_predicate(predicate) do
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case fun.(get(description, triple_predicate)) do
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{objects_to_return, new_objects} ->
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{objects_to_return, put(description, triple_predicate, new_objects)}
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:pop -> pop(description, triple_predicate)
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end
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end
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end
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@doc """
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Pops the objects of the given predicate of a Description.
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When the predicate can not be found the optionally given default value or `nil` is returned.
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# Examples
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iex> RDF.Description.pop(RDF.Description.new({EX.S, EX.P, EX.O}), EX.P)
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{[RDF.uri(EX.O)], RDF.Description.new(EX.S)}
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iex> RDF.Description.pop(RDF.Description.new({EX.S, EX.P, EX.O}), EX.Missing)
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{nil, RDF.Description.new({EX.S, EX.P, EX.O})}
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"""
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def pop(description = %RDF.Description{subject: subject, predications: predications}, predicate) do
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case Access.pop(predications, convert_predicate(predicate)) do
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{nil, _} ->
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{nil, description}
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{objects, new_predications} ->
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{Map.keys(objects), %RDF.Description{subject: subject, predications: new_predications}}
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end
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end
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@doc """
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The set of all properties used in the predicates within a `RDF.Description`.
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# Examples
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iex> RDF.Description.new([
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...> {EX.S1, EX.p1, EX.O1},
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...> {EX.p2, EX.O2},
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...> {EX.p2, EX.O3}]) |>
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...> RDF.Description.predicates
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MapSet.new([EX.p1, EX.p2])
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"""
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def predicates(%RDF.Description{predications: predications}),
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do: predications |> Map.keys |> MapSet.new
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@doc """
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The set of all resources used in the objects within a `RDF.Description`.
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Note: This function does collect only URIs and BlankNodes, not Literals.
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# Examples
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iex> RDF.Description.new([
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...> {EX.S1, EX.p1, EX.O1},
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...> {EX.p2, EX.O2},
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...> {EX.p3, EX.O2},
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...> {EX.p4, RDF.bnode(:bnode)},
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...> {EX.p3, "foo"}
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...> ]) |> RDF.Description.objects
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MapSet.new([RDF.uri(EX.O1), RDF.uri(EX.O2), RDF.bnode(:bnode)])
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"""
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def objects(%RDF.Description{predications: predications}) do
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Enum.reduce predications, MapSet.new, fn ({_, objects}, acc) ->
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objects
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|> Map.keys
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|> Enum.filter(&RDF.resource?/1)
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|> MapSet.new
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|> MapSet.union(acc)
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end
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end
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@doc """
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The set of all resources used within a `RDF.Description`.
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# Examples
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iex> RDF.Description.new([
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...> {EX.S1, EX.p1, EX.O1},
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...> {EX.p2, EX.O2},
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...> {EX.p1, EX.O2},
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...> {EX.p2, RDF.bnode(:bnode)},
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...> {EX.p3, "foo"}
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...> ]) |> RDF.Description.resources
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MapSet.new([RDF.uri(EX.O1), RDF.uri(EX.O2), RDF.bnode(:bnode), EX.p1, EX.p2, EX.p3])
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"""
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def resources(description) do
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description
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|> objects
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|> MapSet.union(predicates(description))
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end
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def triples(description = %RDF.Description{}), do: Enum.to_list(description)
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defdelegate statements(description), to: RDF.Description, as: :triples
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@doc """
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Returns the number of statements of a `RDF.Description`.
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"""
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def count(%RDF.Description{predications: predications}) do
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Enum.reduce predications, 0,
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fn ({_, objects}, count) -> count + Enum.count(objects) end
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end
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@doc """
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Checks if the given statement exists within a `RDF.Description`.
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"""
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def include?(description, statement)
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def include?(%RDF.Description{predications: predications},
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{predicate, object}) do
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with triple_predicate = convert_predicate(predicate),
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triple_object = convert_object(object) do
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predications
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|> Map.get(triple_predicate, %{})
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|> Map.has_key?(triple_object)
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end
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end
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def include?(desc = %RDF.Description{subject: desc_subject},
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{subject, predicate, object}) do
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convert_subject(subject) == desc_subject &&
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include?(desc, {predicate, object})
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end
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def include?(%RDF.Description{}, _), do: false
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# TODO: Can/should we isolate and move the Enumerable specific part to the Enumerable implementation?
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def reduce(%RDF.Description{predications: predications}, {:cont, acc}, _fun)
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when map_size(predications) == 0, do: {:done, acc}
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def reduce(description = %RDF.Description{}, {:cont, acc}, fun) do
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{triple, rest} = RDF.Description.pop(description)
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reduce(rest, fun.(triple, acc), fun)
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end
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def reduce(_, {:halt, acc}, _fun), do: {:halted, acc}
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def reduce(description = %RDF.Description{}, {:suspend, acc}, fun) do
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{:suspended, acc, &reduce(description, &1, fun)}
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end
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def pop(description = %RDF.Description{predications: predications})
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when predications == %{}, do: {nil, description}
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def pop(%RDF.Description{subject: subject, predications: predications}) do
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# TODO: Find a faster way ...
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predicate = List.first(Map.keys(predications))
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[{object, _}] = Enum.take(objects = predications[predicate], 1)
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popped = if Enum.count(objects) == 1,
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do: elem(Map.pop(predications, predicate), 1),
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else: elem(pop_in(predications, [predicate, object]), 1)
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{{subject, predicate, object},
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%RDF.Description{subject: subject, predications: popped}}
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end
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end
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defimpl Enumerable, for: RDF.Description do
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def reduce(desc, acc, fun), do: RDF.Description.reduce(desc, acc, fun)
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def member?(desc, triple), do: {:ok, RDF.Description.include?(desc, triple)}
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def count(desc), do: {:ok, RDF.Description.count(desc)}
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end
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defimpl RDF.Data, for: RDF.Description do
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def add(description, statements), do: RDF.Description.add(description, statements)
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def put(description, statements), do: RDF.Description.put(description, statements)
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def delete(description, statements), do: RDF.Description.delete(description, statements)
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def pop(description), do: RDF.Description.pop(description)
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def include?(description, statements),
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do: RDF.Description.include?(description, statements)
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def statements(description), do: RDF.Description.statements(description)
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def predicates(description), do: RDF.Description.predicates(description)
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def objects(description), do: RDF.Description.objects(description)
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def subjects(%RDF.Description{subject: subject}), do: MapSet.new([subject])
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def resources(%RDF.Description{subject: subject} = description),
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do: RDF.Description.resources(description) |> MapSet.put(subject)
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def subject_count(_), do: 1
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def statement_count(description), do: RDF.Description.count(description)
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end
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