Interaction Model of Pen-and-Paper User Interfaces - Human-Computer Interaction - page 70

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Fig. 3.4 The extended setup of Pen-and-Paper User Interfaces of our concept

3.2 Related Models

Almost all previous research on PPUIs focuses on interaction techniques and sys-
tems, but not on theory. In contrast, in the field of Tangible User Interfaces (TUIs)
- of which PPUIs are a subclass - a growing number of publications address theo-
retical aspects. These concepts of TUIs can be used to theoretically describe partial
aspects of PPUIs. We start by briefly reviewing research on TUIs and then discuss
works on PPUIs that address theoretical aspects of interaction.
Theoretical frameworks of Tangible User Interfaces have made important con-
tributions to the theoretical structuring of the domain by defining main components
and conceptual terms as well as by categorizing systems. We can distinguish the
following main dimensions which are addressed by these frameworks:

1. The coupling between physical and digital input and output
2. The conceptual and perceptual similarities between physical objects and their
digital counterparts
3. The interaction with tangible objects in the physical space

Ullmer and Ishii [158] extend the well-known Model-View-Controller paradigm
[67] to an interaction model for combined physical and digital interfaces. This de-
scribes elements for physical and digital input and output. It carries over the 'model'
and 'control' elements while the 'view' element is divided into two subclasses. This
accounts for the fact that most tangible interfaces represent the model's state by a
combination of physical and digital information. The first subclass of the 'view' el-
ement are tangible objects which represent (parts of) the state of the digital model.
These objects can also act as a physical control for the digital model. Second, a
digital representation can provide further information on the system state, e.g. on
dynamic information which might be hard to express by physical objects. For ex-
ample, this digital representation can be provided on a nearby screen, via a speaker
or by projecting a digital image onto the tangible objects.
Conceptual and perceptual similarities of physical and digital objects are ad-
dressed in Fishkin's taxonomy [29]. It includes two dimensions. The first dimension,