# How to Create a New Entity Type

#### When is needed to create a new entity?

First, check if an existing entity can solve the needed use case to avoid over engineering a solution. If none of the existing entity types defined in <https://github.com/decentraland/common-schemas/blob/main/src/platform/entity.ts#L13> satisfies the requirements, then you may need to create a new entity type.

#### First answer:

* Is the new entity an NFT Collection?
* How will the ownership be validated?
* Which will be the size of it?
* What is the amount entities that will be created?

#### Steps

First create a ADR in <https://github.com/decentraland/adr> where you will define the schema and the date to start validating the new entity.

**Repositories**

**@dcl/schemas**

1. Create the new entity type in the enum: <https://github.com/decentraland/common-schemas/blob/main/src/platform/entity.ts#L19>
2. Create the folder and files in <https://github.com/decentraland/common-schemas/tree/main/src/platform> generating the type and JSON schema, for example: <https://github.com/decentraland/common-schemas/blob/main/src/platform/profile/profile.ts#L20>

**@dcl/content-validator**

Implement the validations defined in the ADR, taking into account the date of that ADR in <https://github.com/decentraland/content-validator/blob/main/src/validations/timestamps.ts>. For example: <https://github.com/decentraland/content-validator/blob/main/src/validations/items/emotes.ts#L8>

1. Add the code to check the ownership of the new entity type in <https://github.com/decentraland/content-validator/tree/main/src/validations/access-checker>
2. Implement the validationForType for the new type, for example: <https://github.com/decentraland/content-validator/blob/main/src/validations/profile.ts#L112>
3. Here you will need to define the max size per entity in <https://github.com/decentraland/content-validator/blob/main/src/validations/ADR51.ts>.

**@dcl/urn-resolver**

1. If the new entity corresponds to a Collection, then nothing has to be added.
2. If not, then create a new urn corresponding to the new entity and define it in <https://github.com/decentraland/urn-resolver> adding a resolver in <https://github.com/decentraland/urn-resolver/blob/main/src/resolvers.ts#L23>

**Catalyst: Content Server**

1. No change in database needed.
2. Update all modified libraries detailed above.

**Catalyst: Lambdas Server**

1. Update all modified libraries detailed above.
2. Check if the profile sanitization needs to be updated (`/lambdas/profiles` endpoint)
3. Check if the erc collections endpoint needs to be updated (`/lambdas/collections` endpoint)
4. Create an endpoint to show that entity, for example `/lambdas/wearables-by-owner`


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