> For the complete documentation index, see [llms.txt](https://docs.neurelo.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.neurelo.com/neurelo-schema-language-nsl/example-2-simple-posts-app.md).

# Example 2 - Simple "Posts" App

This is a simple representative schema for a PostgreSQL datasource, which has 4 objects (tables) - links, posts, topics, users - with relationships between these objects.

### Neurelo Schema

{% code fullWidth="false" %}

```json
{
  "objects": {
    "links": {
      "properties": {
        "id": {
          "type": "integer",
          "default": {
            "function": "autoincrement"
          },
          "identifier": true
        },
        "link": {
          "type": "string",
          "sourceType": [
            "VarChar",
            500
          ],
          "nullable": true
        },
        "title": {
          "type": "string",
          "sourceType": [
            "VarChar",
            500
          ],
          "nullable": true
        },
        "topic_id": {
          "type": "integer",
          "nullable": true
        },
        "topics": {
          "nullable": true,
          "$ref": "#/objects/topics",
          "relation": {
            "attrKey": [
              "topic_id"
            ],
            "foreignAttrKey": [
              "id"
            ],
            "onUpdate": "NoAction",
            "onDelete": "NoAction"
          }
        }
      }
    },
    "posts": {
      "properties": {
        "content": {
          "type": "string",
          "nullable": true
        },
        "id": {
          "type": "integer",
          "default": {
            "function": "autoincrement"
          },
          "identifier": true
        },
        "title": {
          "type": "string",
          "sourceType": [
            "VarChar",
            200
          ],
          "nullable": true
        },
        "user_id": {
          "type": "integer",
          "nullable": true
        },
        "users": {
          "nullable": true,
          "$ref": "#/objects/users",
          "relation": {
            "attrKey": [
              "user_id"
            ],
            "foreignAttrKey": [
              "id"
            ],
            "onUpdate": "NoAction",
            "onDelete": "NoAction"
          }
        }
      }
    },
    "topics": {
      "properties": {
        "description": {
          "type": "string",
          "nullable": true
        },
        "id": {
          "type": "integer",
          "default": {
            "function": "autoincrement"
          },
          "identifier": true
        },
        "links": {
          "type": "array",
          "items": {
            "$ref": "#/objects/links"
          }
        },
        "title": {
          "type": "string",
          "sourceType": [
            "VarChar",
            200
          ],
          "nullable": true
        }
      }
    },
    "users": {
      "properties": {
        "email": {
          "type": "string",
          "sourceType": [
            "VarChar",
            200
          ],
          "nullable": true
        },
        "first_name": {
          "type": "string",
          "sourceType": [
            "VarChar",
            100
          ],
          "nullable": true
        },
        "id": {
          "type": "integer",
          "default": {
            "function": "autoincrement"
          },
          "identifier": true
        },
        "last_name": {
          "type": "string",
          "sourceType": [
            "VarChar",
            100
          ],
          "nullable": true
        },
        "password": {
          "type": "string",
          "sourceType": [
            "VarChar",
            500
          ],
          "nullable": true
        },
        "posts": {
          "type": "array",
          "items": {
            "$ref": "#/objects/posts"
          }
        }
      }
    }
  }
}
```

{% endcode %}