at 20 Years of HCI at York : Kings Manor,
York, 4th June 2004
slides (PDF, 2.6M)
- 20 years on - the PIE and all that
- I started to work in HCI when I joined the "5 man project" in
1985. Part of our aim was to formalise Harold's GUEPs (Generative Usability
Engineering Principles) and this lead to the development of generic models
of classes of interactive system. Unlike specifications of particular systems
these were designed in order to aid understanding of general issues. The PIE
model was the most generic of these taking a minimal view of single-person
interaction: input, output and processing. Despite its simplicity, the PIE
model enabled us to descriptive properties such as WYSIWYG (what you see is
what you get) and also to proof things about undo.
There were numerous variants of the PIE model and related models, perhaps
the most complex being 'the cube', developed with Roberta Mancini. This modelled
'layered' systems where an underlying system had some added higher-level functionality,
allowing is, in particular, to prove more detailed properties of undo and
also to model 'back' and history features in browsers.
Although this is not as central to my work now as it once was, this kind of
modelling has not ceased. As a way of measuring the continued interest in
this sort of formal modelling I looked at citations in citeseer
to my first book (Formal Methods for Interactive Systems). Very much to my
surprise I found that this has remained relatively stable over the period
citeseer covered (1993-2001). Recently too I wrote a chapter of formalism
in HCI for Jack Carroll's theory collection and of course there are several
chapters relating to formal methods in a very successful HCI textbook :-)
This type of formalism is particularly popular in Italy although the Italian
translation perversely has skipped these chapters!
- further back - a formal methods success story
- Strangely my greatest success story in applying formal methods to HCI came
before I went to York! In 1984 I was working in Cumbria County Council
in the Data processing Department and building transaction processing (TP)
systems. Like web-based systems these have a single server with many terminals
submitting screen-forms. In order to make sense of the increasingly complex
programs I used flowchart, not of the program, but of the human-computer dialogue.
At that stage I did not know the words, but I was using a form of formal dialogue
specification. This lead to an enormous productivity gain, but it is only
now, in retrospect, I can see why it was so powerful.
- formal futures - ubiquity and physicality
- The PIE model was about single-user glass screen , keyboard and mouse interaction.
Extensions dealt with multi-user interaction and other topics, but still largely
restricted to standard GUI-style interaction. However, now computers are permeating
every aspect of our lives both at work and at home. Traditional interfaces
tended to be quite broad and shallow in terms of their semantics. For formal
specification this meant that the main advantage of formalism was definitional
- helping clarify understanding. For a mathematician, proofs and analysis
were shallow or trivial. However ubiquitous systems often consist of relatively
simple individual components interacting in relatively complex ways ... just
the sort of thing formalism and mathematics are good at! So formal methods
are more important now than ever.
Working with Masitah Ghazali at Lancaster we are looking 'fluidity' the way
in which the physicality of simple knobs, buttons etc. is exploited in everyday
consumer electronics. The aim is to mine the rich knowledge embodied in these
existing artefacts in order to build transferable design principles for novel
tangible devices. As part of this process we build state diagrams of the physical
device and corresponding state diagrams of the logical functions they control
and relate the two.
Another aspect of ubiquitous interaction is where sensor-based systems do
things 'for you' without bidding. A common example of this is car courtesy
lights which switch themselves on and off when you unlock the car, open doors,
start/stop the engine etc. I call this incidental interaction, although there
are also several other closely related terms in the literature. Given the
relationship between sensors and user activity is uncertain, design methods
must be robust to this uncertainty. This use of sensors and intelligence within
a forgiving interactional context I call 'appropriate intelligence'. As a
first step towards a design methodology with students we have been looking
at scenarios, annotating them with varying levels of desirability of controlled
state (e.g. interior light in car), and then using models of sensor state
in order to match these.
In summary, I conclude that 20 years on ... the PIE is still fresh ;-)
- The PIE model
- A. J. Dix and C. Runciman (1985). Abstract models of interactive
systems. People and Computers: Designing the Interface, Ed.
P. J. &. S. Cook. Cambridge University Press. Pp.13-22.
full paper (html)
- A. J. Dix (1991). Formal Methods for Interactive Systems. Academic
Press. ISBN 0-12-218315-0
- The Cube
- R. Mancini (1997). Modelling Interactive Computing by exploiting
the Undo. Dottorato di Ricerca in Informatica, IX-97-5, Università
degli Studi di Roma "La Sapienza
- A. Dix and R. Mancini (1997). Specifying history and backtracking
mechanisms. In Formal Methods in Human-Computer Interaction,
Eds. P. Palanque and F. Paterno. London, Springer-Verlag. Pp. 1-24.
|| full paper (pdf)
chapter (compressed postscript)
- Recent chapters ...
- A. Dix (2003). Upside down As and algorithms - computational formalisms
and theory In HCI Models, Theories, and Frameworks: Toward an Multidisciplinary
Science. John Carroll (ed.) ISBN 1-55860-808-7. Morgan Kaufman, 2003.
and draft chapter
- Chapters 16, 17 and 18 in A. Dix, J. Finlay, G. Abowd and R. Beale (2004).
Human-Computer Interaction, third edition.
Prentice Hall. ISBN 0-13-239864-8.
HCI book /e3/ web site (slides,
case studies, answers to exercises, full text search of the entire book,
- Success story
- see "Upside down As ..." above
- Formalism in ubiquity
Alan Dix 6/6/2004