datalog.ex

defmodule App.Datalog do
  use DatalogBuilder

  import_rules(App.Account.Rules)
  import_rules(App.Document.Rules)
end

example.ex

## Examples

# Query all fields of all rules within the "account" namespace
{:ok, results} = App.Datalog.query(%{rule_namespace: "account", rule: "*", select: "*"})

# Query specific fields of the "admin" rule across all namespaces
{:ok, results} = App.Datalog.query(%{rule_namespace: "*", rule: "admin", select: [:object_id, :object_relation]})

# Query all fields for a specific rule and namespace
{:ok, results} = App.Datalog.query(%{rule_namespace: "account", rule: "admin", select: "*"})

# Find all admins for a specific department
{:ok, results} = App.Datalog.query(%{rule: "admin", where: %{subject_id: "Department1"}})

rule.yml

namespace account {

    # Entity: Department
    # Relations:
    #   - manages: Users who manage the department
    #   - projects: Projects under the department
    entity department {
        relation managers [user]
        relation projects [project]
    }

    # Entity: Project
    # Relations:
    #   - leads: Users who lead the project
    #   - contributors: Users who contribute to the project
    #   - part_of: The department to which the project belongs
    entity project {
        relation leads [user]
        relation contributors [user]
        relation part_of [department]
    }

    # Entity: Group
    # Relations:
    #   - owns_account: Accounts owned by the group
    entity group {
        relation owns_account [account]
    }

    # Entity: User
    # Relations:
    #   - works_in: Departments where the user works
    #   - member_of: Groups the user is a member of
    entity user {
        relation works_in [department]
        relation member_of [group]
    }

    # Entity: Account
    # No direct relations, but involved in permissions and rules
    entity account {}

    # Permissions/Rules
    #   - admin: Assigned based on department management or project leadership
    #   - owner: Assigned based on group membership and account ownership
    permission admin {
        managers in [department] grants [user]
        leads in [project] grants [user]
    }

    permission owner {
        member_of in [group] and owns_account in [group] grants [user]
    }
}

rules.ex

defmodule App.Account.Rules do
  alias Datalog.Fact
  use DatalogBuilder.Rules, namespace: "account"

  def build("admin", %Fact{object_id: admin, object_relation: "manages", subject_id: department}, %Fact{
        object_id: employee,
        subject_id: department,
        object_relation: "works_in"
      }) do
    %Fact{object_id: admin, object_relation: "admin_of", subject_id: employee}
  end

  def build("admin", %Fact{object_id: admin, object_relation: "leads", subject_id: project}, %Fact{
        object_id: employee,
        subject_id: project,
        object_relation: "contributes_to"
      }) do
    %Fact{object_id: admin, object_relation: "leader_of", subject_id: employee}
  end
  
  def build("owner", %Fact{object_id: user, object_relation: "admin", subject_id: group}, %Fact{
        object_id: group,
        subject_id: account,
        object_relation: "owner"
      }) do
    %Fact{object_id: user, object_relation: "owner_of", subject_id: account}
  end
end