Advancing End User Development Through Metadesign - End User Computing Challenges and Technologies: Emerging Tools and Applications - page 148

activity. As suggested in Petre (1995), they high-
light those kinds of information users consider
important for achieving their tasks, even at the
expense of obscuring other kinds, and facilitate
the problem solving strategies, adopted in the
specific user community. Notations reflect tacit
knowledge shared among users in the community.
Authors build documents in the notation using
their tacit knowledge , and the document can be
understood by readers who possess a similar
knowledge (Schön, 1983). The document conveys
implicit information , which can be elicited only
by readers in the community (Costabile et al.,
2006c). Practitioners should be able to use their
tacit knowledge while interacting with computer
systems. The messages on which interaction is
based should convey implicit information.
Users often complain about the system they
use to perform their work tasks, but they are not
and do not want to become computer experts.
One of the reasons that interactive systems are
unusable is because the system imposes strategies
of task execution alien to users; it drives them
to follow unfamiliar reasoning strategies and to
adopt inefficient procedures. It is well known that
“using the system changes the users, and as they
change they will use the system in new ways”
(Nielsen, 1993, p. 78). In turn, the designer must
evolve the system to adapt it to its new usages;
this phenomenon is called co-evolution of users
and systems (Arondi et al., 2002; Costabile et al.,
2006c). In Bourguin et al. (2001), it is observed
that these new uses of the system determine the
evolution of the user culture and of her or his
models and procedures of task evolution, while
the requests from users force the evolution of the
whole technology supporting interaction.
In order to design a system that meets users'
needs and expectations, we must take into account
the following observations:

but they are concrete and situated in the
specific context, in that they are based on
icons, symbols, and words that resemble and
schematize the tools and the entities that are
to be operated in the working environment.
Such notations emerge from users' practical
experiences in their specific domain of activ-
ity. They highlight those kinds of informa-
tion users consider important for achieving
their tasks, even at the expense of obscuring
other kinds, and facilitate the problem solv-
ing strategies, adopted in the specific user
community.
Software systems are in general designed
without taking into account the problem of
implicit information, user articulatory skills,
and tacit knowledge, so that they can be in-
terpreted with high cognitive costs. Actually,
these factors are among those determining the
so-called invisible work (Nardi & Engeström,
1999). To design and manage organizations
is therefore crucial to understand the nature
and structure of invisible work. Implicit in-
formation, for example, the spatial location
and the physical appearance of the objects of
interest, is often significant only to users who
possess the knowledge to interpret it. Most
of this knowledge is not made explicit and
codified but is tacit knowledge, namely it is
knowledge that users possess and currently
use to carry out tasks and to solve problems,
but that they are unable to express in verbal
terms and that they may even be unaware
of. It is a common experience that in many
application fields, users exploit mainly their
tacit knowledge, since they are often more
able to do that than to explain what they do.
Thus, as suggested in Karasti (2001), “to make
the invisible visible, to tease out the implicit,
complex workplaces need to be investigated
for the practical task-oriented activities” (p.
34). This implies the need of a close observa-
tion of everyday work practice settings, rather

2.

1. The notations developed by the user commu-

nities from their work practice are not defined
according to computer science formalisms,