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3.3 Applying knowledge from the physical world to the digital world 91

management: to capitalize on the "pile" phenomenon by trying to emulate it in
the electronic world. Why not let people arrange their electronic files into piles as
they do with paper files? The danger of doing this is that it could heavily constrain
the way people manage their files, when in fact there may be far more effective
and flexible ways of filing in the electronic world. Mark Lansdale (1988) points
out how introducing unstructured piles of electronic documents on a desktop
would be counterproductive, in the same way as building planes to flap their
wings in the way birds do (someone seriously thought of doing this).
But there may be benefits of emulating the pile phenomenon by using it as a
kind of interface metaphor that is extended to offer other functionality. How might
this be achieved? A group of interface designers at Apple Computer (Mandler et
al., 1992) tackled this problem by adopting the philosophy that they were going to
build an application that went beyond physical-world capabilities, providing new
functionality that only the computer could provide and that enhanced the interface.
To begin their design, they carried out a detailed study of office behavior and ana-
lyzed the many ways piles are created and used. They also examined how people
use the default hierarchical file-management systems that computer operating sys-
tems provide. Having a detailed understanding of both enabled them to create a
conceptual model for the new functionality-which was to provide various interac-
tive organizational elements based around the notion of using piles. These included
providing the user with the means of creating, ordering, and visualizing piles of
files. Files could also be encoded using various external cues, including date and
color. New functionality that could not be achieved with physical files included the
provision of a scripting facility, enabling files in piles to be ordered in relation to
these cues (see Figure 3.8).
Emulating real-world activity at the interface can be a powerful design strat-
egy, provided that new functionality is incorporated that extends or supports the
users in their tasks in ways not possible in the physical world. The key is really to
understand the nature of the problem being addressed in the electronic world in re-
lation to the various coping and externalizing strategies people have developed to
deal with the physical world.

portable computer

Figure 3.8 The pile metaphor as it appears at the interface.