docs/HowItWorks.md

---
id: how-it-works
title: How it Works
---

In Casbin, an access control model is abstracted into a CONF file based on the **PERM metamodel (Policy, Effect, Request, Matchers)**. So switching or upgrading the authorization mechanism for a project is just as simple as modifying a configuration. You can customize your own access control model by combining the available models. For example, you can get RBAC roles and ABAC attributes together inside one model and share one set of policy rules.

The most basic and simplest model in Casbin is ACL. ACL's model CONF is:

```ini
# Request definition
[request_definition]
r = sub, obj, act

# Policy definition
[policy_definition]
p = sub, obj, act

# Policy effect
[policy_effect]
e = some(where (p.eft == allow))

# Matchers
[matchers]
m = r.sub == p.sub && r.obj == p.obj && r.act == p.act

```

An example policy for ACL model is like:

```
p, alice, data1, read
p, bob, data2, write
```

It means:

- alice can read data1
- bob can write data2

We also support multi-line mode by appending '\\'  in the end:  

```ini
# Matchers
[matchers]
m = r.sub == p.sub && r.obj == p.obj \ 
  && r.act == p.act
```

Further more, if you are using ABAC,  you can try operator `in` like following in Casbin **golang** edition (jCasbin and Node-Casbin are not supported yet):

```ini
# Matchers
[matchers]
m = r.obj == p.obj && r.act == p.act || r.obj in ('data2', 'data3')
```

But you **SHOULD** make sure that the length of the array is **MORE** than **1**, otherwise there will cause it to panic.

For more operators, you may take a look at [govaluate](https://github.com/Knetic/govaluate)