Behaviour for defining custom repository types with extensible graph catalogs.

DCATR.Repositorys are the core catalog layer in DCAT-R. This behaviour enables applications to create specialized repository types with custom graph collections and selector logic.

Graph Structure

A repository contains:

• dataset - Primary catalog of DataGraphs (user data)
• manifest_graph - Repository manifest (RepositoryManifestGraph)
• system_graphs - Optional repository-level graphs (e.g., history, provenance)

Callbacks

• system_graphs/1 - Returns additional system-level graphs
• primary_graph/1 - Returns the primary graph if one is designated

Inherits from DCATR.Directory.Type:

• DCATR.Directory.Type.graphs/1, DCATR.Directory.Type.directories/1

Inherits from DCATR.GraphResolver:

• DCATR.GraphResolver.resolve_graph_selector/2

Standard Selectors

• :primary - Primary graph (when present)
• :repository_manifest, :repo_manifest - Repository metadata graph

Usage

Custom repository types should use DCATR.Repository.Type and define a Grax schema extending DCATR.Repository:

defmodule MyApp.Repository do
  use DCATR.Repository.Type

  schema MyApp.NS.Repository < DCATR.Repository do
    link history_graph: MyApp.NS.history(), type: MyApp.HistoryGraph
  end

  @impl true
  def resolve_graph_selector(repo, :history), do: repo.history_graph
  def resolve_graph_selector(repo, selector), do: super(repo, selector)

  @impl true
  def system_graphs(repo) do
    [repo.history_graph | super(repo)]
  end
end

The module automatically provides delegating implementations of all callbacks and convenience functions, all of which are overridable.