Interaction Model of Pen-and-Paper User Interfaces - Human-Computer Interaction - page 69

In the setup depicted on the left hand side, digital pen and paper serve as a pure
input channel to feed data into the digital system. Optionally, the system provides
feedback via a separate channel. This is typically realized by a nearby display of a
computer, a mobile phone, a PDA, or a projector, but the PPUI might also use audi-
tory or haptic output channels. Hence, the PPUI can span several devices. The right
hand side of the illustration depicts a different basic setup: Data is not processed on
a backend system, but directly on the pen. Optionally, feedback is provided directly
by the pen using a built-in display, audio feedback, a built-in projector or haptic
output channels.
This basic setup considers only individual users. Yet, as we have discussed in
Section 1.1, paper is a collaborative medium. Multiple physical objects in the phys-
ical space serve co-located interaction very well since they provide multiple points
of interaction. Figure 3.3 depicts three settings that exemplify how several users can
collaborate with one or multiple paper media. Paper media can be easily reposi-
tioned and combined, which provides for flexible collaborative settings. In a collab-
orative PPUI, several users can share the same paper interface or use different paper
objects. Multiple pens can be used simultaneously, on a single or on multiple sheets
of paper.
While paper is a very adequate medium for co-located collaboration, it is difficult
to use paper for collaboration over distance. PPUIs can address this challenge and
enable users to collaborate over distance not only by using digital but also by us-
ing physical documents. Two or more collaborators work at different locations and
possibly at different points in time. Each user works on his or her local physical or
digital representation of the document. Modifications that a person makes to a paper
document are automatically distributed to his or her collaborators over a network
connection and made digitally available (e.g. in a software viewer, by projecting
changes onto the paper document or by reprinting the paper document).
Figure 3.4 depicts the collaborative setup of the Pen-and-Paper User Interface
which we will present Chapters 4-7. Users can work individually, can share docu-
ments over a network connection and can cooperate in a co-located setup. The setup
combines digital pens and paper with a PC, laptop or an interactive tabletop display.

One Group Multiple Groups Individual Users

Fig. 3.3 Multiple points of interaction enable various co-located collaborative settings