When a transaction is sent to the blockchain in order to change the value at a specific path in the blockchain state, it needs to be sent with a digital signature created with the private key corresponding to an account who has the permission to write the value to the path. More specifically, permission of the database path is controlled by owner and rule which can be also modified by signed transactions. While owner permission at a path is granted by specifying certain actionable types (i.e. branch_owner, write_function, write_owner, write_rule) to accounts, rules are more flexible and can be used with conditional statements. The details are covered in the rules section.