Abstract: In a multi-user environment, a method of controlling access to objects is required, such that updates performed by one user are not overwritten by simultaneous updates by another user. There is provided a method of controlling access to objects and containers, each representing a group of objects, in a multi-user environment whereby lock states of the objects and lock states of the containers are stored in a computer system, said method comprising the steps of: accepting a request for access to an object or a container; deciding access based on the lock state for that object or container, the lock state of a container if the request is for an object contained within that container, and the lock state of objects grouped within a container if the request is for a container object; and sending a message to the requester granting or denying access to said object or container object. Updates performed by one user on an object or a container are not overwritten by simultaneous updates by another user.