Constructing and enforcing access control policies

1. A method comprising:

receiving a schema of user interface comprising an arrangement of interface elements, each element configured to display data from cells of a database;

receiving a user permission for the user interface, the user permission specifying one or more users allowed to access the user interface;

receiving an element permission for an interface element of the user interface, the element permission specifying data of the interface element accessible to users of the user interface;

generating a policy object for the user interface based on the user permission and the element permission, the policy object specifying which cells of the database can be accessed by the user interface;

receiving a query from a client device associated with a user to implement a local instance of the user interface; and

serving the query according to the policy object, wherein serving the query comprises providing data from the database that the user interface provides access to without providing other data from the database that should not be accessible according to the policy object.

2. The method of claim 1 , further comprising:

receiving an update to one or more cells of the database;

generating a customized payload for the client device according to the policy object, the customized payload indicating changes to the one or more cells of the database that the user of the client device is authorized to access according to the policy object; and

transmitting the customized payload to the client device, the customized payload enabling the client device to update the local instance of the user interface.

3. The method of claim 2 , wherein generating the customized payload for the client device comprises:

aggregating the update and additional updates to cells of the database into a payload; and

removing updates in the payload that the user of the client device is not authorized to access according to the policy object.

4. The method of claim 1 , wherein the policy object is a list of rules specifying which cells of the database can be accessed by each of the one or more users.

5. The method of claim 1 , wherein the policy object prevents the client device associated with the user from accessing cells of the database the user is not authorized to access.

6. The method of claim 1 , wherein the policy object comprises a dependency graph.

7. The method of claim 6 , serving the query according to the policy object comprises traversing the dependency graph to determine whether the user has access to a cell specified in the query.

8. The method of claim 1 , further comprising:

receiving an update to the schema of the interface; and

determining the update renders the policy object inadequate.

9. The method of claim 8 , further comprising: responsive to determining the update renders the policy object inadequate, rendering the policy object invalid.

10. The method of claim 8 , further comprising: updating the policy object based on the update responsive to determining the update renders the policy object inadequate.

11. The method of claim 8 , further comprising: generating a new policy object based on the update responsive to determining the update renders the policy object inadequate.

12. The method of claim 1 , further comprising:

receiving multiple queries requesting access to cells of the database; and

processing the multiple queries sequentially in a queue according to the policy object.

13. The method of claim 12 , wherein responsive to determining a first query in the queue affects a dependency of the policy object, delaying processing subsequent queries in the queue until the policy object is updated or a new policy object is generated.

14. The method of claim 13 , further comprising processing the subsequent queries in the queue according to the updated policy object or the new policy object, wherein processing the subsequent queries in the queue comprises denying a subsequent query in the queue according to the updated policy object or the new policy object, wherein the subsequent query would have been accepted according to the policy object.

15. A non-transitory computer-readable storage medium storing instructions that, when executed by a computing system, cause the computing system to perform operations comprising:

receiving a schema of user interface comprising an arrangement of interface elements, each element configured to display data from cells of a database;

receiving a user permission for the user interface, the user permission specifying one or more users allowed to access the user interface;

receiving an element permission for an interface element of the user interface, the element permission specifying data of the interface element accessible to collaborators of the user interface;

generating a policy object for the user interface based on the user permission and the element permission, the policy object specifying which cells of the database can be accessed by the user interface;

receiving a query from a client device associated with a user to implement a local instance of the user interface; and

serving the query according to the policy object, wherein serving the query comprises providing data from the database that the user interface provides access to without providing other data from the database that should not be accessible according to the policy object.

16. The non-transitory computer-readable storage medium of claim 15 , further comprising:

receiving an update to one or more cells of the database;

generating a customized payload for the client device according to the policy object, the customized payload indicating changes to the one or more cells of the database that the user of the client device is authorized to access according to the policy object; and

transmitting the customized payload to the client device, the customized payload enabling the client device to update the local instance of the user interface.

17. The non-transitory computer-readable storage medium of claim 16 , wherein generating the customized payload for the client device comprises:

aggregating the update and additional updates to cells of the database into a payload; and

removing updates in the payload that the user of the client device is not authorized to access according to the policy object.

18. The non-transitory computer-readable storage medium of claim 15 , wherein the policy object is a list of rules specifying which cells of the database can be accessed by each of the one or more users.

19. The non-transitory computer-readable storage medium of claim 15 , wherein the policy object prevents the client device associated with the user from accessing cells of the database the user is not authorized to access.

20. The non-transitory computer-readable storage medium of claim 15 , wherein the policy object comprises a dependency graph.