# This class models a vertex in a directed graph.
class Vertex < ActiveRecord::Base
  has_many :sink_edges, :class_name => "Edge", :foreign_key => "source_id"
  has_many :sinks, :through => :sink_edges

  has_and_belongs_to_many :sources,
    :class_name => "Vertex", :join_table => "edges",
    :foreign_key => "sink_id", :association_foreign_key => "source_id"
end