# Data Model

If you want to start contributing data to FrontierNav, it is worth knowing how the data is structured.

FrontierNav uses a graph data model for its data which consists of the following concepts. Depending on where and how they are used, they can use different names but still mean the same thing.

* Entity Type (Table, Category, Relation, Schema)
* Relationship Type (Inner Table, Nested Table)
* Property (Column, Field, Attribute)
* Entity (Row, Entry, Page, Tuple, Node, Vertex)
* Relationship (Link, Reference, Edge)
* Data (Cell, Value)

## Entity Type (Category)

Entity Types *define* the structure of Entities using Properties. An Item is an Entity Type, whereas a Small Potion is an Entity.

Entity Types are called Categories throughout FrontierNav for familiarity with other wiki software.

## Relationship Type

Relationship Types *define* a link between two Entity Types in one direction. So **Enemies drop Items** and **Items are dropped by Enemies** is one Relationship Type as they mean the same thing but are read in opposite directions.

The first Entity Type *owns* the Relationship Type, so it can point to as many other Entity Types as it wants. However, the linked Entity Types can only point to the first. So Enemies can drop Items and Weapons, but Weapons can't then be dropped by Treasure Chests. To do that, you will need another Relationship Type owned by Treasure Chests. This limitation was introduced to simplify the model a bit to avoid many-to-many spaghetti. This may change in the future as FrontierNav improves its tooling.

## Property

Properties *define* the structure of an Entity's Data. For example, an Item has a **price** which is a **number**.

Properties can also *define* the structure of a Relationship's Data. For example, an Enemy drops an Item at a certain **rate**.

### Property Types

The types of values Properties can define are currently limited to the following:

* Text ("Hello", "A sentence", **string**)
* Number (0, 1, 2, 3, **number**)
* Boolean (yes/no, true/false, **boolean**)
* Relationship (references a RelationshipType)
* Tunnel (references a Relationship Property **entrance** and a corresponding Property **exit**)
  * Useful for re-using data from other Entity Types without having to repeat yourself.
* Attachment (references a file like an **image**)

## Entity

An Entity is something that *exists* in the game world. A Character, Item, Enemy, Mission are all Entity Types, whereas "The Hero", "Small Potion", "Defeat the Dragon" respectively are Entities.

## Relationship

A Relationship *links* two Entities together. Both Entities will refer to the Relationship in their Data to link them together. For example, **Black Dragons drop Dragon Scales**.

## Data

Data *describes* an Entity. Where Properties define the structure of Data, Data contains the values. For example, a Small Potion has a **price** of **200** gold.

Similarly, Data helps *describe* a Relationship: Black Dragons have an **80%** chance to drop Dragon Scales.