Extending procedural task models by systematic explicit integration of objects, knowledge and information

Task analysis can be considered as a fundamental component of user centered design methods as it provides a unique way of analyzing in a systematic way users' roles and activities. A widely used way of storing the information gathered during that phase in a structured and exhaustive way is to build task models which are then amenable to verification of properties or to performance evaluation. In widely used notations such as Hierarchical Task Analysis (HTA) or CTT (Concur Task Tree), information or objects manipulated by the users while performing the tasks does not receive a similar treatment as the sequencing of tasks which is usually carefully and exhaustively described. This paper proposes a systematic account for the various concepts manipulated by the users while performing tasks. Such concepts include different types of knowledge (declarative, situational, procedural and strategic), objects (manipulated by the user) and information. These concepts are systematically represented in a set of extensions of the HAMSTERS notation allowing the analysis of concepts-related properties such as learning curve, complexity, information workload,... We demonstrate the application of the approach on the example of a two players game making explicit the connection between these extended task models and the user interface of the game.