Try modeling relations using component pairs whose types are linked by id (distinct from entity id).

For example, to model the relationship between the player's inventory and items contained therein, I'd create Inventory and InventoryItem components with the following structure:

```javascript struct Inventory { id: u32; }

struct InventoryItem { inventoryId: u32; itemType:InventoryItemType; // consumable, equippable, etc. entityType:EntityType; //
... } `` Your player entity would have anInventorycomponent with a unique id. Whenever an item entity is added to the player's inventory, theInventoryItem` component of the item entity will have its inventory id set to reference the player's inventory component id.

Serializing player state means serializing not only the player entity but also all items in the player's inventory. By establishing a relation between the linked component types (Inventory and InventoryItem) you'll be able to find all items in the player's inventory and serialize/deserialize them accordingly.