,--------------.              
|article       |  ,----------.
|--------------|  |resource  |
|NODE          |  |----------|
|published_date|  |NODE      |
|categories    |  |categories|
|listings      |  |listings  |
`--------------'  `----------'
                              
                              
  ,----------.     ,--------. 
  |page      |     |category| 
  |----------|     |--------| 
  |NODE      |     |NODE    | 
  |is_listing|     `--------' 
  `----------'