A Task Model Based On Perceptual Control Theory And Its Application In User Interface Development

Nowadays,as the role of computing devices has changed from being the professionalized tools for office workers to being life assistants for the general public,the application of computing devices has expanded from desktop work to all aspects of human's lives.Because of the diversity of users,hardware and software platform(s),and environment,the development of the interactive system is facing new challages on usability,i.e.the development of user interfaces to meet specific needs for users with different knowledge,skills,and preferences,to keep interfaces consistent and easy to use,even for devices with different physical attributes(screen size,CPU,memory),and to make it adaptable to non-office environment with various factors(noise,light,location information)affecting the completion of tasks.With the increasing complexity of the context of use(user,platform,environment),a high usability interface has become one of the key factors for the business success of interactive systems.In order to improve the usability of interface development,a common practice in Human Computer Interaction is to transform the task model to the interface model of differing abstraction levels based on the analysis and modeling of user tasks,and to generate the final user interface(semi-)automatically.It is generally agreed that an effective and efficient interactive system with high user satisification can be developed with this user-centered method.However,in the mobile computing environment,the diversity of users and the platforms,as well as the complexity of the environment,has led to great changes of the characteristics of user tasks.Most of the current task modeling methods,generated in the era of desktop systems and even in the era of command line interfaces,are not capable of describing the user tasks completely in the mobile computing environment.Therefore,this paper argues that the backwardness of user task modeling technology accounts for the inability of generating a high usability interface with the model-based interface development method and for the failure of wide usage in the industry.In this paper,a method of user task modeling for mobile computing is proposed,and then the application of this method to user interface development is studied.The specific contents and innovation achievement are as follows:(1)In order to better describe the user task of mobile computing environment,a Perceptual-Control-Theory-Based Task Analysis(PCTBTA)method is propsed in the paper.The analysis and modeling process in PCTBTA method relies on a perceptual-control-based task modeling framework to support user-centered design and user interface development.The characteristics of PCTBTA method are mainly manifested in the following points:Firstly,the Perceptual Control Theory(PCT)is used as the psychological base for user task analysis and modeling processes.Secondly,PCTBTA task model explicitly introduces "external influences" and"display variables",with the former leading designers to bring the context information into task model,thus extending its scope of description,and the latter reflecting the interactive content at a higher abstraction level,thus providing the task space for usability design of user interface.Thirdly,according to the features of user tasks in mobile computing environment,a task description unit of user's target hierarchy,Perceptual Control Task Unit(PCTU),is proposed,providing foundation for building interfaces to cope with the dynamic environment flexibly.(2)This paper provides a set of graphical task notations with semantics to accurately record the analysis results of PCTBTA method.The graphical task notations can not only represent the general task sequence,but also describe task sets that are sensitive to the context and that are used to deal with abnormal situations.This symbolic representation provides a common communication language for users,designers and developers.(3)This paper proposes a method transforming PCTBTA task model to interface model.The process consists of three stages.Firstly,the task sets that can be logically presented on the same interface are extracted from the PCTBTA task model.Secondly,the task sets are transformed to the dialog model.Thirdly,the dialog model is transformed to the interface model.(4)A prototype of the task modeling tool that supports the PCTBTA method has been developed.In accordance with PCTBTA's analytical ideas,the tool provides designers with graphical editing interfaces for a clearer and smoother analysis process.In addition,the tool also provides the functionality to export graphical description of task model to an XML-based description,which makes it possible to transfrom the models with other tools.