User tasks modeling has been the focus of many research works either for designing user interfaces suitable to given use cases or for identifying the current task of the user in order to assist him/her. The problem of user tasks modeling has been widely addressed within the context of GUIs (Graphical User Interfaces). In this paper, we present an overview of several existing task models and we discuss the specificities of user tasks modeling in the context of Ambient Intelligent Environments, which are mainly place-related tasks, device-related tasks and the possible errors occurring while performing a task. Then, we discuss the limitations of the classical user tasks models and depict the requirements of a task model specific to an interaction with an ambient environment.