fostering a positive attitude toward the demonstrator
system (also cf. works on apparent usability, as, e.g.,
in (Kurosu and Kashimura, 1995)). (4) Finally, the
alignment principal concerns the relative placement
of visual affordances on a graphical screen. Broadly
speaking, related elements in the design should be
aligned with related elements to create a sense of
unity, cohesion or semantic relatedness (as is, for ex-
ample, the case with medical pictures of body regions
which exhibit a spatial relationship). All principles
should help to diminish the degree of misuse and mis-
understanding based on the described factors.
Usability Strategy. Design principles can become
manifest in a specific usability strategy. Broadly
speaking, these strategies try to improve the user-
friendliness and efficiency of a prototype. General
usability guidelines further express that a usable prod-
uct is easy to learn, efficient to use, provides quick
recovery from errors, is easy to remember, enjoyable
to use, and visually pleasing. While these guidelines
provide a nice abstract list of optimisation parameters,
experience shows they are only seldom used to go
through the prototype development cycle, as (Cron-
holm, 2009) points out. The analysis and design prin-
ciples described in the previous paragraph offer more
technical advice when following the development cy-
cle.
We used the analysis and design guidelines in
combination with usability guidelines that consider
five different planes (Garrett, 2002) in the develop-
ment process. Every plane has its own issues that
must be considered. From abstract to concrete, these
are (1) the strategic plane, (2) the scope plane, (3) the
structure plane, (4) the skeleton plane, and (5) the sur-
face plane. In accordance with the software develop-
ment process in figure 3, defining the users and their
needs on the strategic plane is the first step in the de-
sign process. It is also useful to create personas that
represent a special user group, e.g., the representa-
tives of a specific business case. On the scope plane,
then, you have to define the system’s capacity (e.g.,
what a user should be able to say when using a mul-
timodal Internet terminal for music download and ex-
change, cf. figure 7(3)) and then the requirements for
the technical dialogue components.
4.2 Implementation
In the implementation stage, we rely on the specifi-
cation of the strategic and scope planes according to
the specific use case or demonstration workflow and
the resulting dialogue shell requirements for the up-
per three planes, and we implement the functional
components while taking the design principles into
account (figure 4). The broad accessibility princi-
ple applies to the scope plane where the functional
specifications and interface content requirements are
met. Interestingly, the alignment principle often ap-
plies to the structure plane, i.e., the information archi-
tecture. According to the Semantic Web data speci-
fications (RDF/OWL), we try to encode as many re-
lationships for the concepts as possible. This means,
e.g., in the context of medical images (figure 7, 3),
that specific body regions have spatial relationships.
These relationships can then be seen as an image
alignment and used to influence/specify the layout
on the skeleton plane. The 80/20 rule principle on
the skeleton plane essentially provides a recommen-
dation for the implementation of the multimodal in-
put possibilities. It specifies that 20 percent of the
input possibilities should be available to the user at
first sight. This way of modelling is particularly in-
teresting in speech-based interaction systems. Al-
though a 20 percent selection of graphical interface
elements and functions is easily conceivable, the re-
striction of speech-based commands to a specific sub-
set is counter-intuitive. Nonetheless, state-of-the-art
ASR systems can be tuned to recognise speech utter-
ances in context. Accordingly, we modelled our ASR
and multimodal input integration components to work
particularly robustly for approximately 20 percent of
the input possibilities. This is particularly beneficial
in demonstration scenarios since it can reduce the er-
ror rate while the presenter gains external control of
the demonstration session.
The aesthetic effect principle applies to the sur-
face plane and the visual design of the graphical in-
terface. In many use case specific software envi-
ronments, both corporate identity and native applica-
tion side conditions hinder a proper implementation
of this principle. For example, the mobile GUI in fig-
ure 7(2) is mostly driven by the other applications on
the iPhone which a business expert uses for his daily
work. In this situation, a good trade-off must be found
and usability studies can deliver the necessary empir-
ical indication. The situation is different for pure re-
search prototypes that exhibit a new interaction form.
Aesthetic designs are generally perceived as easier to
use which has significant implications regarding ac-
ceptance; figure 7(3) shows a multimodal interface
where the aesthetic effect principle has been obeyed
with much care.
We implemented an abstract container concept
called Semantic Interface Elements (SIEs) for the rep-
resentation and activation of multimedia elements vis-
ible on the different interface devices. Semantic-
based data integration frameworks for multimedia
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