Introduction - Human-Computer Interaction - page 12

Fig. 1.2 A digital pen (Anoto ADP-301, copyright Anoto)
PPUIs have the advantage that the technology is available on the market, afford-
able and can be easily integrated into established work practices. Moreover, writing
with a pen is one of the most important forms of working with documents. Digital
pens retain the flexibility of free-form input, which is central to knowledge acqui-
sition as we have discussed above. PPUIs can be realized with several different pen
technologies. Each of them has different advantages and drawbacks. We will discuss
these technologies in the following chapter. The currently most advanced technol-
ogy is Anoto Digital Pen and Paper [4]. Figure 1.2 depicts an Anoto pen.
In the example shown above in Fig. 1.1, a PDF document is printed on several pa-
per sheets. All interactions that the user makes with the pen on these paper sheets are
automatically captured and interpreted by the computer system. On the one hand,
the digital pen can be used for annotating the document. Handwritten annotations
that are made on the printed version of the document are automatically integrated
into the digital document. On the other hand, each sheet of paper contains addi-
tional user interface elements. Several interactive areas behave like virtual buttons.
When the user taps with the pen on one of these buttons, a command is triggered.
For instance, the buttons allow the user to categorize annotations with a label and
share them with co-workers. Feedback is given directly on the pen and on a nearby
computer display. A digital version of the document can be accessed on the display,
including handwritten annotations and their categories. If necessary, the user can
also print an updated version of the document.
A frequent use case of PPUIs consists of annotating printed versions of digital
documents, as outlined in the example above. PPUIs are also used to augment tradi-
tional paper notebooks with digital functionality. While the paper notebook retains
many of the advantages of paper (e.g. mobile use, intuitive handwriting), a digital
version is automatically created that includes additional functionality (e.g. digital
images can be directly integrated into the notebook). As a further sample use case,
PPUIs allow us to design paper-based controls for computer systems. For instance,
pen and paper can be used as a remote control for a TV set. These are only some ap-