Introduction - Human-Computer Interaction - page 10

with ease, to efficiently organize information in space, and to effectively communi-
cate.
Motivated by the workplace studies from the literature and a number of own
studies in which we analyzed how university students use paper and digital media
[145, 144, 143, p. 19 sqq.], we are strongly convinced that rather than replacing pa-
per, combining paper with computers is more promising. This combines the ease and
flexibility of using paper with the powerful capabilities of computing. It is left to the
user to choose the adequate medium for a given task. Several technical approaches
allow for combining paper with digital documents:
Printing and Scanning A first approach consists of using two well-established
tools for bridging between both worlds: printers and scanners. If a printed version
of a digital document is required, the user prints it. In the reverse direction, if a
digital version of some paper document is required, the document is scanned. These
tools are quite powerful for one-way transformations. However, this is different once
the user wants to perform a cyclic transformation. Imagine that the user prints a
document on paper, makes handwritten annotations, and then wants to integrate
these annotations back into the digital version. Such a process is difficult and time-
consuming to perform. Moreover, scanning has a low update rate and therefore does
not allow more interactive uses of paper that have immediate effects on the digital
side.
Interactive Paper Another class of approaches extends the user interface of a com-
puter system to paper. Thereby physical paper becomes interactive. Interacting on
or with paper does not only alter the physical paper sheet, but also controls the com-
puter system. Interactive paper is often understood as synonymous to using a digital
pen on physical paper. The digital pen behaves like a traditional pen and leaves
visible, physical ink traces on paper. In addition, the pen captures the traces elec-
tronically and sends them to a computer system. The traces can be visualized as a
facsimile of the handwritten content or can be interpreted as commands for control-
ling the computer system. In addition to pen input, some interactive paper systems
also identify whether paper documents are present and how they are arranged to
react accordingly on the digital side. For instance, a camera tracks the location of
paper documents on a desk and captures their contents. A projector projects ad-
ditional digital information onto the same surface [167]. As another example, the
detailed arrangement of several paper documents on an interactive tabletop controls
how digital information is laid out on the surface [57].
Electronic Paper Whereas interactive paper solutions use real paper, electronic
paper [16] is a novel display technology. It provides for very thin, bendable and
lightweight displays. Even though these displays are not paper, they share many of
its physical characteristics. Currently the development of electronic paper is in a
rather early stage. Electronic paper displays available on the market are still rigid
and quite thick. Hence, many of the affordances of paper that we have identified
in the previous section are not reached yet. While it can be expected that this will
change in the future, there will be many years to come until electronic paper can be