Chapter 7: Synthesizing Good Design--Principles and Patterns

In the last three chapters, we've discussed a process through which we can achieve superior interaction design. But what makes a design superior? Design that meets the goals and needs of users (without sacrificing business goals or ignoring technical constraints) is one measure of design superiority. But what are the attributes of a design that enable it to accomplish this successfully? Are there general, context-specific attributes and features that a design can possess to make it a "good" design?

The authors strongly believe that the answer to these questions lies in the use of interaction design principles—guidelines for design of useful and useable form and behavior, and also in the use of interaction design patterns—exemplary, generalizable solutions to specific classes of design problem. This chapter defines these ideas in more detail. In addition to design-focused principles and patterns, we must also consider some larger design imperatives to set the stage for the design process. These are addressed at the end of this chapter.

Interaction Design Principles

Interaction design principles are generally applicable guidelines that address issues of behavior, form, and content. They represent characteristics of product behavior that help users better accomplish their goals and feel competent and confident while doing so. Principles are applied throughout the design process, helping us to translate tasks that arise out of scenario iterations into formalized structures and behaviors in the interface.

Principles minimize work

One of the primary purposes principles serve is to optimize the experience of the user when he engages with the system. In the case of productivity tools and other non—entertainment-oriented products, this optimization of experience means the minimization of work (Goodwin, 2002a). Kinds of work to be minimized include:

• Logical work—comprehension of text and organizational structures

• Perceptual work—decoding visual layouts and semantics of shape, size, color, and representation

• Mnemonic work—recall of passwords, command vectors, names and locations of data objects and controls, and other relationships between objects

• Physical/motor work—number of keystrokes, degree of mouse movement, use of gestures (click, drag, double-click), switching between input modes, extent of required navigation

Most of the principles in this book attempt to minimize work while providing greater levels of feedback and contextually useful information up front to the user.

Principles operate at different levels of detail

Design principles operate at three levels of organization: the conceptual level, the interaction level, and the interface level. This book addresses all three levels to some degree, although the focus is on interaction-level principles.

• Conceptual-level principles help define what a product is and how it fits into the broad context of use required by its primary personas. Chapters 3, 8, and 9 discuss conceptual-level design principles.

• Interaction-level principles help define how a product should behave, in general, and in specific situations. The chapters in Parts II, III, V, VI, and VII discuss general interaction-level principles, and Part VIII discusses interaction-level principles for the Web and device interfaces.

• Interface-level principles help define the look and feel of interfaces. Part IV and some of the chapters in Parts V and VI contain interface-level principles.

Most interaction design principles are cross-platform, although some platforms, such as the Web and embedded systems, have special considerations based on the extra constraints imposed by that platform.

Principles versus style guides

Style guides rather rigidly define the look and feel of an interface according to corporate branding and usability guidelines (see Chapter 19 for further discussion of look-and-feel issues). They typically focus at the detailed widget level: How many tabs are in a dialog? What should button highlight states look like? What is the pixel spacing between a control and its label? These are all questions that must be answered to create a finely tuned look and feel for a product, but they don't say much about the bigger issues of what a product should be or how it should behave.

The authors recommend that designers pay attention to style guides when they are available and when fine-tuning interaction details, but there are many bigger and more interesting issues in the design of behavior that rarely find their way into style guides. Most of the remainder of this book provides just such guidelines for the design of well-behaved interactive systems. They include principles and some patterns as well, but are not specified in terms of any particular style guide. The remainder of this chapter and both Section Two and Section Three of this book seek to address these bigger issues of what makes good behavior.