Transportable applications environment (TAE) PLUS: Experiences in "Object"ively modernizing a user interface environment

Abstract

This paper describes the evolution of the Transportable Applications Executive (TAJZ) (developed at NASA/Goddard Space Flight Center) from a traditional procedural menu and co-doriented 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 programner 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 corwnand language that provides cormnds for displaying and manipulating interaction objects, thus providing a means to quickly prototype an application's user interface. During TAE Plus develqment, many design and implementation decisions were based on the stateof- the-art within graphics workstations, windowing systems and object-oriented programning 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 Smalltalkn' language to prototype the initial WorkBench; why C++ was selected (over other languages) to build the WorkBench; and experiences in using X Window SystemTM and Stanford's Interviews object library The paper concludes with open issues and a description of the next steps involved in implementing the "totally modem" TAE.