Modeling Roles

Roles are a common way to group users and assign permissions to those groups. They can be used to simplify permission management, especially in larger systems where many users have similar access needs.

In this guide, we'll explore common approaches to modeling roles with OpenFGA.

When to Use Each Approach

Before diving into implementation details, here's a quick guide to help you choose the right approach:

Approach	Best For	Complexity	Flexibility	Example
Relations as Roles	Static, predefined roles	Low	Low	In all instances, company admins can view project information.
Simple User-Defined Roles	User-defined roles at org level	Medium	Medium	Company Acme creates an "Auditor" role that is configured to view project information for all projects.
Role Assignments	Instance-specific role assignments	High	High	In Company Acme, Anne can be a custom Auditor role for Projects 1 and 5, but Beth can be an Auditor on Project 3.

Approach 1: Relations as Roles

The simplest way to implement roles is to use directly assignable relations. They work well for roles that always exist and can be defined at development-time. Adding relations is straightforward, and you do not need to add roles very frequently. If roles are static, this is always the preferred approach.

Example: Organization Admin Role

In the model below, we define an admin role at the organization level. Admins can edit billing details and create projects.

model
  schema 1.1

type user

type organization
  relations
    define admin: [user]
    define can_create_project: admin
    define can_edit_billing_details: admin

Adding Users to Roles

To add users to the admin role, create a tuple like:

- user: user:anne
  relation: admin
  object: organization:acme

Extending with Additional Roles

If later you need to add a project_admin role with permissions to view/edit projects, the model evolves to:

model
  schema 1.1

type user

type organization
  relations
    define admin: [user]
    define project_admin: [user]  # new role

    # existing permissions
    define can_edit_billing_details: admin 
    define can_create_project: admin or project_admin

    # new permissions for project admins
    define can_edit_project: admin or project_admin
    define can_view_project: admin or project_admin

Pros and Cons

✅ Advantages:

• Simple to implement and understand
• Fast evaluation performance
• Clear authorization policies
• No additional tuples needed when adding permissions
• Role permissions are straightforward to change, regardless of scale

❌ Disadvantages:

• Roles must be predefined in the model
• Not suitable for user-defined roles

---

Approach 2: Simple User-Defined Roles

Many applications require the flexibility for end-users to define their own custom roles, in addition to any pre-defined roles. This approach enables organizations to tailor permissions to their specific needs.

Example: Custom Project Admin Role

With the following model, your application can support both static roles and user-defined roles:

model
  schema 1.1

type user

type role
  relations
    define assignee: [user]

type organization
  relations
    define admin: [user]  # static role

    # permissions can be assigned to custom roles or static roles
    define can_create_project: [role#assignee] or admin 
    define can_edit_project: [role#assignee] or admin 

Setting Up Custom Roles

1. Define role permissions by creating tuples that grant the role-specific permissions:

- user: role:acme-project-admin#assignee
  relation: can_create_project
  object: organization:acme

- user: role:acme-project-admin#assignee
  relation: can_edit_project
  object: organization:acme

2. Assign users to the role:

- user: user:anne
  relation: assignee
  object: role:acme-project-admin

Adding New Permissions

When you add new permissions to your model, existing roles don't automatically receive them:

model
  schema 1.1

type user

type role
  relations
    define assignee: [user]

type organization
  relations
    define admin: [user]
    define can_create_project: [role#assignee] or admin 
    define can_edit_project: [role#assignee] or admin 
    define can_delete_project: [role#assignee] or admin  # new permission

To grant the new permission to existing roles, create additional tuples:

- user: role:acme-project-admin#assignee
  relation: can_delete_project
  object: organization:acme

You do not need to add these tuples when adding the new permission. End-users will add the new permission to their custom roles when they find it appropriate.

Pros and Cons

✅ Advantages:

• Supports user-defined roles
• Flexible permission assignment
• No model changes needed for new role instances

❌ Disadvantages:

• More complex than static relations
• Requires additional tuples for role-permission mapping

---

Approach 3: Role Assignments

The previous approach works well when custom roles are global for the organization. However, if you need roles that can be attached to different object instances with different members for each instance, you need role assignments.

Example: Project-Specific Admin Roles

Let's say you want a "Project Admin" role where each project can have different admins, but the role permissions remain consistent.

Step 1: Define the Role and its Permissions

Define a role type where you list all the permissions that any role can have:

model
  schema 1.1

type role
  relations
    define can_view_project: [user:*]
    define can_edit_project: [user:*]

A "Project Admin" role can have can_view_project and can_edit_project:

# Project Admin role has both the can_view_project and can_edit_project assigned
- user: user:*
  relation: can_view_project
  object: role:project-admin

- user: user:*
  relation: can_edit_project
  object: role:project-admin

Step 2: Assign Users to a Role on an Entity

Add a role_assignment type to assign users to the role:

type role_assignment
  relations
    define assignee: [user]
    define role: [role]

    define can_view_project: assignee and can_view_project from role
    define can_edit_project: assignee and can_edit_project from role

Step 3: Connect to Your Objects

Define an organization type with an admin role. Then, define a project type that links to an organization and a role_assignment. Note that we are combining a static admin role with custom role assignments. We recommend to always use static roles when they are known in advance.

type organization 
  relations
    define admin: [user]

type project
  relations
    define organization: [organization]
    define role_assignment: [role_assignment]
    
    # combine role assignments and static roles
    define can_edit_project: can_edit_project from role_assignment or admin from organization
    define can_view_project: can_view_project from role_assignment or admin from organization

Setting Up Role Assignments

1. Create the role assignment instance:

- user: user:anne
  relation: assignee
  object: role_assignment:project-admin-openfga

- user: role:project-admin  
  relation: role
  object: role_assignment:project-admin-openfga

2. Link the role assignment to the project:

- user: role_assignment:project-admin-openfga
  relation: role_assignment
  object: project:openfga

3. Link the project to an organization:

- user: organization:acme
  relation: organization
  object: project:openfga

Pros and Cons

✅ Advantages:

• Maximum flexibility for instance-specific roles
• Reusable role definitions across different objects
• Fine-grained control over role membership

❌ Disadvantages:

• Most complex approach to implement
• Requires careful planning of the role hierarchy
• More tuples needed for setup and maintenance

---

Choosing the Right Approach

Decision Tree

1. Do you need user-defined roles?

   • No → Use Relations as Roles
   • Yes → Continue to step 2

2. Do roles need different members per object instance?

   • No → Use Simple User-Defined Roles
   • Yes → Use Role Assignments

Performance Considerations

• Relations as Roles: Fastest evaluation
• *Simple User-Defined Roles: Moderate performance impact
• Role Assignments: Highest performance impact

Best Practices

1. Start simple: Begin with relations as roles and evolve as needed
2. Hybrid approach: Combine static relations for well-known roles with dynamic roles for custom ones
3. Documentation: Clearly document your role model for your team
4. Functional Testing: Write tests to verify your model behaves as expected
5. Performance Testing: Test performance with realistic data volumes

Related Sections

Check out these related resources for more information about adopting OpenFGA.

Custom Roles Step by Step

Follow a detailed walkthrough of implementing custom roles.

• More

Multi-tenant RBAC Example

See a complete multi-tenant role-based access control implementation.

• More

Role Assignments Example

Explore a full role assignments implementation.

• More