An Approach To Evaluating User Interfaces For Usability Based On Perceptual Control Theory

In process of software system development, the software quality evaluation is indispensable. Because before the development, user's potential requirements may not be completely understood by designer, so the software development is an evaluation centered iterative process. Evaluation aims to discover the design problems and the user demand that not been modeling in software prototype, and solved in the iterative design process. The user interface as users and system's interactions platform, the quality of interaction design will affect system usability, namely how the services that the system provided can easily be used by users. Therefore, usability evaluation is an important activity in the process of interaction design.As for traditional word processing tasks, usability principles emphasize to provide the appropriate information representation and proper operating mode, or correct "Look-and-Feel", aim to satisfy users' requirements of efficiently and effectively. The traditional usability evaluation method mainly consider whether the system can easily build users an accurate operation sequences, which is used to evaluate system availability. Today, however, complex computing environment caused by predefined orderly operation is not necessarily can effectively control system state. In other words, the "correct" sequence of operations may not effectively and efficiently bring the results that user required. So, in the static environment, the interface characteristics that the traditional user interface evaluation method concerned is no longer appropriate.With the development of information technology, personal computing has evolved into social computing, user and system no longer in a relatively static environment. Rapidly changing environment makes users cannot control system state changes by prediction, System must be able to dynamically provide the key features of their own state change and the operation sets that can let user make the right choice, to help user complete their tasks. So, in this dynamic environment, system evaluation should mainly concern system state transfer and user's control. Based on such a dynamic environment, In this paper, we present an evaluation methods which based on perceptual control theory-PCTEM, this method introduce psychological perceptual control theory in to interface evaluation method. Perceptual control theory believe that all behavior is from the perception of control, applied it to the interface evaluation, consider whether the user interface state can easily be understood by user, namely, whether interface elements reflect information that the users want to control. Firstly, in dynamic environment, PCTEM according to the current state of systems and users to evaluate interface, namely evaluate the state of the interface. Secondly, the evaluator is user, not usability specialists, this can guarantee the user interface is user centered from source. Finally, in the evaluating process, take the external interference into account. In order to validate the feasibility and effectiveness of the new evaluation method, this paper evaluated a well-known airplane ticket system interface, to find the interface usability problems, and give corresponding modification.