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The authors of [50] have identified some requirements of
systems for the development of user interfaces (UIs): consideration of
standards, openness to all interaction styles, and provision of comfortable
design tools. They argue that most of the existing systems fulfill only
some of those requirements. Therefore, they present a layered model for the
interface between an application's functionality and its UI which will
especially be useful for the design of UIs for multi-tasking,
multi-windowing systems that support a free choice of input and output
media. Two pictures shown in figure 4.3 are best suited to
show their approach.
Figure 4.3
: The basic software architecture (left picture) and the
corresponding layered model for human-computer interaction (right
picture). (Adapted from [50])
By introducing these layers, the authors want to achieve ``a clear
separation of application functionality from dialog functionality, and a
clear responsibility for the different actions that are involved in a
dialog.'', i.e. different actions are located in different layers. The
responsibilities (and functionalities, resp.) have been defined as follows:
- presentation layer:
- output to the screen; handling of inputs from
the user; toolkit functionalities
- virtual presentation layer:
- separation of input and output [...]
from the dialog; definition of logical devices and virtual terminals;
machine- and device-independent presentation; handles all static aspects
of the UI
- virtual application layer:
- contains the semantics of the respective
application; dialog between the user and the application; handles all
dynamic aspects of the UI
- application layer:
- application's functionality
Another aspect of this implementation is the object-oriented approach
which allows the layers to communicate via messages. Such a
well-defined, layered model seems to be a good approach for an independent,
thus flexible implementation of a human-computer interface which can also
be used for a multimodal application.
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Esprit Project 8579/MIAMI (Schomaker et al., '95)
Thu May 18 16:00:17 MET DST 1995