Human-computer interaction

Abstract

Human-computer interaction (HCI) is a multidisciplinary field "concerned with the design, evaluation and implementation of interactive computing systems for human use and with the study of major phenomena surrounding them" [24]. A human-computer system1 is typically made up of two components: the user interface and the functional core. The user interface captures user input and turns it into calls to the functional core, which typically implements the algorithmic component of the system. The user interface also turns the results of its calls to the functional core into output to be presented to the user. A human-computer system therefore interacts with its user(s) through its user interface. Human-computer systems are arguably the first truly interactive systems. In 1963, Ivan Sutherland's SketchPad [48] was the first system to use pen input on a CRT display, pioneering direct manipulation techniques that are still in use today. Forty years later, millions of people interact with graphical user interfaces on daily basis, to the point where computers are often reduced to their input-output devices and applications to their user interface. Yet human-computer systems are still created at great cost with algorithmic approaches. More than a decade ago, a study showed that on average 50% of the development cost of human-computer systems is spent on the user interface [37]. One of the main reasons was the lack of proper tools to develop such interfaces, their growing complexity and the inability to test them thoroughly. There is no reason to believe that the situation has changed substantially since then because the tools in use today are based on the same concepts as twenty years ago. User interfaces are notoriously difficult to program, debug and maintain because they exacerbate many aspects of interactive systems. For example, traditional interactive systems, i.e., systems that interact with other computer systems, often rely on well-specified protocols so that it is fairly easy to anticipate future possible inputs. uman-computer systems, for they have a human in the loop, cannot rely on such strict protocols. In order to give the user a sense of control, they must be prepared to receive virtually any input at any moment, and react to it in a way that will be understandable to the user. Therefore the state space of a human-computer system is extremely large. This chapter evaluates some unique aspects of human-computer systems with respect to the five characteristics of interactive systems outlined in the preface of this book: • Nonalgorithmic computational problem: human-computer systems are often created by turning an algorithmic system into an interactive one in order to give the users more control over the process; at the same time, many human-computer systems are not meant to solve a particular algorithmic problem but instead to extend human capabilities in order to address more open-ended situations. • Dynamic interleaving of user input and system output streams: human- computer systems feature intricate dependencie between input and output streams, with tight timing constraints and large abstraction mismatches between user, streams and computer. • Dependency on the environment: the evolution towards novel forms of interaction, such as ubiquitous and pervasive computing, mixed and augmented reality, and tangible interfaces, extends the environment of human- computer systems to the physical world and blurs the distinction between physical and digital artifacts. • Parallel "computation" of user and computer : the unique characteristics of human users as well as the distributed nature of many interfaces require multiple threads and various levels of parallelism and synchronization between user and computer. • Noncomputability of the environment : humans are inherently noncomputable, but the learning and adaptation capabilities of users and computers can be leveraged to create more powerful human-computer systems. The chapter covers a wide range of user interface styles and techniques, from traditional graphical user interf ces to advanced research, and considers the full life-cycle of human-computer systems from design to evaluation. © 2006 Springer-Verlag Berlin Heidelberg.