| Systems design is a very analytical way of approaching design problems; it uses an established arrangement of components to create design solutions. Whereas in user-centered design, the user is at the center of the design process, here a systema set of entities that act upon each otheris. A system isn't necessarily a computer, although it can be. Systems can also consist of people, devices, machines, and objects. Systems can range from the simple (the heating system in your house) to the enormously complex (whole governments). Systems design is a structured, rigorous design methodology that is excellent for tackling complex problems and that offers a holistic approach to designing. Systems design doesn't discount user goals and needsthey can be used to set the goal of the system. But in this approach, users are deemphasized in favor of context. Designers using systems design focus on the whole context of use, not just individual objects or devices. Systems design can be thought of as a rigorous look at the broad context in which a product or service will be used. Systems design outlines the components that systems should have: a goal, a sensor, a comparator, and an actuator. The job of the designer, then, becomes designing those components. In this way, systems design eliminates the guesswork and fuzziness of the other approaches and provides a clear roadmap for designers to follow. Let's use the classic example of a heating system to illustrate the main parts of any system (Figure 2.3). Figure 2.3. A system, based on a diagram by Hugh Dubberly and Paul Pangaro, 2003. 
Goal. This is not the users' goal, but rather the goal of the system as a whole, which can be drawn from user goals. The goal states the ideal relationship between the system and the environment it lives in. In a heating system, an example of a goal is keeping your house at 72 degrees Fahrenheit. Environment. Where does the system "live"? Is it digital or analog or both? The environment in the heating system example is the house itself. Sensors. How does the system detect changes in the environment? A heating system has a thermostat with a thermometer (Figure 2.4) to detect temperature changes. Disturbances. Changes are called disturbances; these are elements in the environment that change the environment in both expected and unexpected ways. In the heating system example, a disturbance is a drop in temperature. More on disturbances in a moment. Comparator. The comparator embodies the goal within the system. It compares the current state (the environment) to the desired state (the goal). Any difference between the two is seen by the system as an error, which the system seeks to correct. In the heating system example, the comparator can be a tiny computer or a mercury switch that compares what the sensor tells it about the environment (for example, "72 degrees...72 degrees...72 degrees...71 degrees...71 degrees") to the goal ("Keep the house at 72 degrees"). Actuator. If the sensor detects a disturbance, the comparator says, ah, something is different (an "error"), and it sends a command to the actuator (in this case, the boiler). Actuators are a means of making changes (output) to the environment. In this case, the actuator makes heat. Feedback. With output comes feedback. Feedback is a message about whether or not a goal was achieved or maintainedwhether or not an error was detected. In the heating system example, feedback would report either that the house is still at 71 degrees or that it is now at 72 degrees and the heater can be turned off. Controls. Controls are means of manually manipulating the parts of the system (except the environment). In this example, you use a control to set the temperature you want the house to be. Another control might trigger the actuator and turn the heat on.
Figure 2.4. A thermostat contains the sensor, comparator, actuator, and controls of a heating system. 
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There are two types of disturbances to the environment that may affect our heating system. The first consists of expected disturbances, such as the periodic drops in temperature. The second type consists of unexpected disturbancesthings that fall outside of the expected range of input. These types of disturbances typically cause the system to crash or behave in odd ways. In our heating example, such an event might be a sudden 100-degree drop in temperature. To make most unexpected disturbances expected (and thus make the system more stable), systems need what's called requisite variety. The system needs an assortment of responses to deal with a range of situations. These responses can be anything from error messages ("You are being sent 1 million e-mail messages!"), to workarounds ("You are being sent 1 million e-mail messages. Should I delete them or deliver them in chunks of 10,000?"), to mechanisms to prevent the system from failing (deleting all incoming e-mails over a certain number). Systems without requisite variety crash often, which may be fine for a prototype, but not so great for, say, an air-traffic control system. Feedback is output from the system that reports that something has just happened: input was received from the environment, the comparator was changed, and so on. You get feedback from your computer almost every time you press a key. We'll discuss feedback in more detail in Chapter 3, but we'll simply note here that systems without feedback either will not work or will be bewildering. Systems design isn't only about digital products, of course. Most services (see Chapter 8), for example, are systems consisting of digital and analog components. Your local coffee shop is filled with sensors, comparators, and actuators, only you probably know them as the shop employees. However, the objections and distaste many designers have about systems design spring from examples just such as these. Many designers feel that systems design is dehumanizing, turning people into robotic components in a very synthetic arrangement. And indeed, systems design is a very logical, analytical approach to interaction design. Emotions, passion, and whim have very little place in this sort of design, except as disturbances in the environment that need to be countered. Someone screaming angrily in the coffee shop is a major disturbance! Systems design's greatest strength, however, is that it is useful for seeing the big picturefor providing a holistic view of a project. No product or service exists in a vacuum, after all, and systems design forces designers to take into account the environment that the product or service inhabits. By focusing on the broad context of use and the interplay of the components, designers gain a better understanding of the circumstances surrounding a product or service. Hugh Dubberly on Systems Design 
courtesy of Thomas Hobbs Hugh Dubberly is founder and principal at Dubberly Design Office (DDO), an interaction design consultancy in San Francisco. Before forming DDO, he served as vice president for design at AOL/Netscape and as creative director at Apple Computer, Inc. He has also taught at San Jose State University and Stanford University. What is systems design? Systems design is simply the design of systems. It implies a systematic and rigorous approach to designan approach demanded by the scale and complexity of many systems problems. Where did systems design come from? Systems design first appeared shortly before World War II as engineers grappled with complex communications and control problems. They formalized their work in the new disciplines of information theory, operations research, and cybernetics. In the 1960s, members of the design methods movement (especially Horst Rittel and others at Ulm and Berkeley) transferred this knowledge to the design world. Systems design continues to flourish at schools interested in design planning and within the world of computer science. Among its most important legacies is a research field known as design rationale, which concerns systems for making and documenting design decisions. What can designers learn from systems design? Today, ideas from design methods and systems design may be more relevant to designers than ever beforeas more and more designers collaborate on designing software and complex information spaces. Frameworks suggested by systems design are especially useful in modeling interaction and conversation. They are also useful in modeling the design process itself. What is the most important thing to be aware of in systems design? A systems approach to design asks: For this situation, what is the system? What is the environment? What goal does the system have in relation to its environment? What is the feedback loop by which the system corrects its actions? How does the system measure whether it has achieved its goal? Who defines the system, environment, goal, and so onand monitors it? What resources does the system have for maintaining the relationship it desires? Are the resources sufficient to meet the system's purpose?
Is systems design incompatible with user-centered design? A systems approach to design is entirely compatible with a user-centered approach. Indeed, the core of both approaches is understanding user goals. A systems approach looks at users in relation to a context and in terms of their interaction with devices, with each other, and with themselves. What is the relationship between systems design and cybernetics? Cybernetics (the science of feedback) provides an approach to systems and a set of frameworks and tools. Among the most important ideas for designers: Definition of a system depends on point of view (subjectivity). We are responsible for our actions (ethical stance). All interaction is a form of conversation. All conversation involves goals, understandings, and agreements.
Are there times when systems design isn't appropriate? A systems approach to design is most appropriate for projects involving large systems or systems of systems. Such projects typically involve many people, from many disciplines, working together over an extended period of time. They need tools to cope with their project's complexity: to define goals, facilitate communications, and manage processes. Solo designers working on small projects may find the same tools a bit cumbersome for their needs. |
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