The evolution of the Common User Access Workplace Model - Technical

IBM Systems Journal,  Sept, 1992  by Richard E. Berry,  Cliff J. Reeves

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This paper describes some of the influences contributing to and issues in dealing with the evolution of user interface guidelines over time. In particular, we focus on the evolution of IBM's user interface architecture, the Common User Access[TM] (CUA[TM]) interface, over a period of six years. Discussed are the key architectural and design elements of the CUA Workplace Model, the fundamental shifts in computer-human interaction that have occurred since the first publication of the guidelines in 1987, and how user interface design, operating systems, and tools have interacted in the evolution of the guidelines.

The information should help designers of user interfaces and developers of user interface guidelines to appreciate some of the factors involved in the long-term evolution of a user interface style. The paper provides an introduction to the most recent evolutionary step in the CUA style (the Workplace Model) to help the reader place these factors in perspective relative to the degree of evolutionary change.

User interface guidelines are intended to help product designers and developers create a user interface that users will find easy to learn and use. The user interface is the means by which users and computers communicate with each other. It supports a dialog, much like a conversation between people, but this dialog occurs between a user and a computer.

The Common User Access(*1) (CUA(*1)) interface guidelines are based on sound user interface design principles and object-oriented relationships. They specify common user interface components and techniques, and guidelines for applying them.

The CUA interface guidelines are general guidelines that are intended to apply to aspects that are common across many products. However, applying these guidelines alone is not enough. Many aspects of a user interface for a product pertain to specific product functions and are not addressed by generalized user interface (UI) design guidelines. These are considered product-specific aspects of the user interface. Two important points to remember regarding product-specific aspects are:

* Generalized guidelines, such as CUA guidelines, should not limit product design creativity and ingenuity for product-specific design issues. For example, IBM's CUA guidelines[1] do not provide direction about how an accounting product should implement a balance sheet or how formulas are handled in a spreadsheet.

* To make good decisions for product-specific design issues, designers need to understand user interface design principles, models, and methods, in addition to applying the CUA guidelines. The user interface design principles, models, and methods described in IBM CUA publications[1,2] are generally applicable to product-specific interface aspects as well.

Evolution of the CUA guidelines

Three publications containing CUA guidelines have appeared in 1987, 1989, and 1991, respectively. The guidelines have changed in response to two related factors: the fast-growing technology of the personal computer, and increasing demand from users that the computer match their way of thinking, rather than the other way around.

The CUA interface has always emphasized the user's needs, but with different assumptions about the technology that would meet them. The guidelines appearing in 1987 (CUA87), for example, assumed a world of personal computers intermixed with host-attached nonprogrammable terminals, like the IBM 3270 Information Display System. CUA87 had a goal of consistency and transfer of a user's knowledge between those systems. But personal computer technology and capabilities advanced rapidly in the 1980s and the gap between how a user could interact with a terminal and what was possible using a personal computer began to widen significantly.

The CUA interface was updated in 1989 (CUA89) to separate and focus on the guidelines that are unique to the needs of a personal computer user. CUA89 applied the principles inherent in CUA87 to a personal computer environment that provided a rich set of user interface mechanisms, like sizable and movable windows, standard menus, user interface controls, and dialogs. Equally as important, the personal computer operating system, exemplified by OS/2(*1) and the Presentation Manager(*1), offered a graphical view of available programs and data, and the ability to run multiple applications concurrently. The user was no longer constrained to working with one application at a time, within the limitations of character-based presentation. Suddenly all of the resources of a powerful system were available to users.

The 1991 guidelines (CUA91) built on this advancement, with tools and techniques that moved the interface closer to the way users accomplish work in the real world. Together, the CUA interface and the OS/2 Workplace Shell(*1) redefine data and application programs to create a set of familiar user objects, and provide the ability for users to utilize these objects in ways that support a variety of users' tasks.