Specification of Reactive Hardware/Software Systems - Electronic ...

4 Introduction
Models, that are adequate for the area sketched, show various internal structures. Most
important are hierarchical structures of interconnected subsystems, functions, transformations
and objects. Hierarchy is a powerful concept for handling complexity. It enables
abstraction and hiding of details. Inevitably the structures created during modelling
influence the implementation structure of the system. This biases the implementation
without taking possible implementation problems into account. We observed that in
practice the implementation structure deviates from the specification model structure.
Especially when developing an implementation independent specification, it is necessary
to maintain the specification model, because a one to one mapping is necessary to
create a consistent whole of various forms of documentation. Maintenance of a specification
model leads to expensive and time consuming iterations. These iterations must
be prevented as much as possible. They disturb the design process. Limiting iterations
in product development processes is therefore an important research goal.
1.1.2 Scientific aspects
Object-Orientation
Reuse and the power to encapsulate behaviour into autonomous entities was the most
striking reason to develop a new method based on the object-oriented paradigm. There
is growing interest in the object-oriented paradigm. Object-orientation is recommended
for reusability and seems to be promising. Earlier research programs in our research
group led to the development of object-oriented design tools targeting at ASIC development
[Ver92]. This was also a reason to focus on object-orientation. A new specification
method could take advantage of a smooth path to hardware design if we are able to
interface with these tools. Concerning specification techniques, we started from our
experience with SASD techniques.
Both structured analysis and object-oriented analysis have their merits. There is no
agreement on the possibilities of integrating class based object-oriented analysis with
the event-oriented approach of structured analysis. This problem is discussed in the
panel discussion ’From Events to Objects: The heresy of Event-Orientation in a World of
Objects’ [C
92]. In fact this is a problem we must solve. Where object-oriented analysis
traditionally focuses on static abstractions in the form of ’real world’ objects, eventorientation
emphasises behaviour as the ’principal guide to successful object-oriented
analysis and design.’
Another challenge is that there is far less consensus in the world of object-orientation
than one might expect. There is no straightforward way to integrate the strengths of
various paradigms and methods. Therefore we looked for a more fundamental approach
than creating a new version of existing approaches. We decided to carry out research at
a conceptual level. Breaking down methods to the finest grains (the concepts), yields an
in depth knowledge. This enables the sound synthesis of a new method by selecting and
combining appropriate concepts. However, the requirements for the new method should
not be determined by a scientific viewpoint only. Industrial needs and the purpose of
the method in its application environment, should also play a very important role.