Entries in the ACL configure the permissions for subjects. A subject is identified by an arbitrary ID.

Authorization Subject

A subject can have following type of permission: read, write, administrate.

  • A subject that has READ permission is allowed to read all data of a Thing, i.e. its Attributes, Features and ACL.
  • WRITE permission is required to be able to set data of the Thing or to send messages to a Thing or Feature.
  • To be able to modify the ACL itself, a subject needs ADMINISTRATE permission.

When a Thing is initially created at least one entry of the ACL with READ, WRITE and ADMINISTRATE permission is mandatory and must be provided. If there is no ACL provided when creating a new Thing, a default ACL will be created. The default ACL entry consists of a subject ID (e.g. the ID of the currently logged in user), and all 3 permissions.

Also, there must always be at least one entry with all permissions. The last entry cannot be deleted or changed to not include all permissions.


Allows to read a Thing. This includes reading its ACL, Attributes, Features and their Properties.

The forwarding of messages to Subscribers is also secured according to the ACL entries on the Things themselves. E.g. only entities with READ permission on the Thing will be notified about changes related to that Thing and its Features.


Allows to write/modify a Thing. E.g. create/update/delete Things, Attributes, Features and their Properties, execute Feature operations.

In order to send messages towards to or receive messages from a Thing one would need WRITE permission on the specific Thing.


Allows to modify the ACL of a Thing and to create/modify/delete its entries according to the restrictions mentioned before.

Example for an Access Control List

The following example shows the ACL JSON object of a Thing.

The first authorization subject is the ID of the default nginx user “ditto”. The second one is the ID of another user “adam” who additionally has WRITE and ADMINISTRATE permission.

"acl": {
  "ditto": {
    "READ": true,
    "WRITE": false,
    "ADMINISTRATE": false
  "adam": {
    "READ": true,
    "WRITE": true,
    "ADMINISTRATE": true
Tags: model