09-11-2012, 02:08 PM
Human Computer Interaction – Lecture Notes
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What is HCI / Interaction Design?
With the exception of some embedded software and operating system code, the success of a
software product is determined by the humans who use the product. These notes present
theoretical and practical approaches to making successful and usable software. A usercentred
design process, as taught in earlier years of the tripos and experienced in many
group design projects, provides a professional resource to creating software with
functionality that users need. However, the availability of technical functionality does not
guarantee that software will be practically usable. Software that is usable for its purpose is
sometimes described by programmers as “intuitive” (easy to learn, easy to remember, easy
to apply to new problems) or “powerful” (efficient, effective). These terms are vague and
unscientific, but they point in the right direction. This course presents scientific approaches
to making software that is “intuitive” and “powerful”.
HCI helps us to understand why some software products are good and other software is
bad. But sadly it is not a guaranteed formula for creating a successful product. In this sense
it is like architecture or product design. Architects and product designers need a thorough
technical grasp of the materials they work with, but the success of their work depends on
the creative application of this technical knowledge. This creativity is a craft skill that is
normally learned by working with a master designer in a studio, or from case studies of
successful designs. A computer science course does not provide sufficient time for this kind
of training in creative design, but it can provide the essential elements: an understanding of
the user’s needs, and an understanding of potential solutions.
Visual representation.
How can you design computer displays that are as meaningful as possible to human
viewers? Answering this question requires understanding of visual representation – the
principles by which markings on a surface are made and interpreted.
Note: many illustrations referred to in this section are easily available online, though with a
variety of copyright restrictions. I will show as many as possible in the lecture itself – if
you want to investigate further, Google should find most of those mentioned.
Typography and text
For many years, computer displays resembled paper documents. This does not mean that
they were simplistic or unreasonably constrained. On the contrary, most aspects of modern
industrial society have been successfully achieved using the representational conventions of
paper, so those conventions seem to be powerful ones. Information on paper can be
structured using tabulated columns, alignment, indentation and emphasis, borders and
shading. All of those were incorporated into computer text displays. Interaction
conventions, however, were restricted to operations of the typewriter rather than the pencil.
Each character typed would appear at a specific location. Locations could be constrained,
like filling boxes on a paper form. And shortcut command keys could be defined using
onscreen labels or paper overlays. It is not text itself, but keyboard interaction with text that
is limited and frustrating compared to what we can do with paper (Sellen & Harper 2002).
Maps and graphs
The computer has, however, also acquired a specialised visual vocabulary and conventions.
Before the text-based ‘glass teletype’ became ubiquitous, cathode ray tube displays were
already used to display oscilloscope waves and radar echoes. Both could be easily
interpreted because of their correspondence to existing paper conventions. An oscilloscope
uses a horizontal time axis to trace variation of a quantity over time, as pioneered by
William Playfair in his 1786 charts of the British economy. A radar screen shows direction
and distance of objects from a central reference point, just as the Hereford Mappa Mundi of
1300 organised places according to their approximate direction and distance from
Jerusalem. Many visual displays on computers continue to use these ancient but powerful
inventions – the map and the graph. In particular, the first truly large software project, the
SAGE air defense system, set out to present data in the form of an augmented radar screen
– an abstract map, on which symbols and text could be overlaid. The first graphics
computer, the Lincoln Laboratory Whirlwind, was created to show maps, not text.
Schematic drawings
Ivan Sutherland’s groundbreaking PhD research with Whirlwind’s successor TX-2
introduced several more sophisticated alternatives (1963). The use of a light pen allowed
users to draw arbitrary lines, rather than relying on control keys to select predefined
options. An obvious application, in the engineering context of MIT, was to make
engineering drawings such as a girder bridge (see figure). Lines on the screen are scaled
versions of the actual girders, and text information can be overlaid to give details of force
calculations. Plans of this kind, as a visual representation, are closely related to maps.
However, where the plane of a map corresponds to a continuous surface, engineering
drawings need not be continuous. Each set of connected components must share the same
scale, but white space indicates an interpretive break, so that independent representations
can potentially share the same divided surface – a convention introduced in Diderot’s
encyclopedia of 1772, which showed pictures of multiple objects on a page, but cut them
loose from any shared pictorial context.