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