Okay, so you've purchased a graphical user interface (GUI) builder tool to help you quickly build a sophisticated user interface, and your developers promise to follow a particular style guide (e.g., OSF/Motif, Apple/Macintosh) when creating the GUI. This is definitely a step in the right direction, but it is no guarantee that the application's user interface will be usable; that is, where the user interface helps, rather than hinders, the end-users from doing their jobs. Numerous techniques for testing the usability and user satisfaction of an application's GUI are available, such as design walk-throughs, field testing with beta releases, demonstrations of prototypes to future end-users, and user questionnaires. One of the most effective techniques is usability testing with defined tasks and metrics, and yet, it is not commonly used in project development life cycles at the National Aeronautics and Space Agency (NASA). This paper discusses a low-budget, but effective, approach we used at NASA's Goddard Space Flight Center (GSFC) to perform structured usability testing. It did not require any additional staff or a usability laboratory, but did successfully identify problems with the application's user interface. The purpose of the usability testing was two-fold: (1) to test the process used in the usability test; and (2) to apply the results of the test to improving the subject software's user interface. This paper will discuss the results from the test and the lessons learned. It will conclude with a discussion of future plans to conduct cost benefit analysis and integrate usability testing as a required step in a project's development life cycle.

The Transportable Applications Environment Plus (TAE Plus) is a NASA-developed user interface development environment (UIDE) for the rapid prototyping, evaluation, implementation, and management of user interfaces. TAE Plus provides an intuitive What You See Is What You Get (WYSIWYG) WorkBench for designing an application's user interface. The WorkBench supports the creation and sequencing of displays, including real-time, data-driven display objects. Users can define context-sensitive help for a target application. They can rehearse the user interface and also generate code automatically. In addition TAE Plus contains application services for the runtime manipulation and management of the user interface. Based on Motif and the MIT X Window System, TAE Plus runs on a variety of Unix- or VMS-based workstations. TAE Plus is an evolving system. User-defined requirements and new technology guide the development of each new version. Advances in virtual operating systems, human factors, computer graphics, command language design, standardization, and software portability are monitored and incorporated as they become available.

TAE Plus was built at NASA's Goddard Space Flight Center to support the building of GUI user interfaces for highly interactive applications, such as realtime processing systems and scientific analysis system. TAE Plus is designed as a productivity tool for the user interface designer. Human factor experts and user interface designers frequently do not want to have to learn the programming details of the windowing environment before they use a GUI development tool to prototype and/or develop an application's user interface. TAE Plus has been developed with this user in mind. TAE Plus is a user interface management system that supports (1) interactively constructing the visual layout of an application screen, (2) rehearsing the UI, (3) generating the application source code to manage the UI, (3) generating the application source code to manage the UI, and (4) providing run-time services to manage the UI during application execution.

This paper describes the evolution of the Transportable Applications Executive (TAE) (developed at NASA/Goddard Space Flight Center) from a traditional procedural menu and command-oriented system to an object-oriented, modeless user interface management system, known as TAE Plus. The impetus for developing this environment and early experiments which led to its current implementation are addressed. The current version of TAE Plus provides design and prototyping functions, working in tandem with a mature application management system. The main components are (1) a user interface designers' WorkBench that allows an application developer to interactively layout an application screen and define the static and/or dynamic areas of the screen; (2) an application programmer subroutine package that provides runtime services used to display and control WorkBench-designed “interaction objects” on the screen; and (3) an extension to the existing TAE command language that provides commands for displaying and manipulating interaction objects, thus providing a means to quickly prototype an application's user interface. During TAE Plus development, many design and implementation decisions were based on the state-of-the-art within graphics workstations, windowing systems and object-oriented programming languages, and this paper shares some of the problems and issues experienced during implementation. Some of the topics discussed include: lessons learned in using the Smalltalk™ language to prototype the initial WorkBench; why C++ was selected (over other languages) to build the WorkBench; and experiences in using X Window System™ and Stanford's InterViews object library. The paper concludes with open issues and a description of the next steps involved in implementing the “totally modern” TAE.