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

36 Concepts for Analysis, Specification and Design
We would like to formalise a specification as early as possible. However, analysis requires
primarily communication with principals, users of the system to be designed
and various experts. This communication is in the form of discussions supported by
narrative descriptions and graphical models. These graphical models must be understandable
for a broad audience. The rather informal character of the analysis phase
requires dedicated concepts for description of the problem domain at a high level of
abstraction. To obtain a precise specification, the informal views must be consistently
accompanied by precise descriptions in a formal language. This formal language must
be able to describe the system entities as well as their behaviour and structure. Therefore
the language should itself be based upon appropriate language concepts. The meaning
of these language concepts (language primitives) must be precisely defined in a
mathematical semantical model of the language.
Besides concepts needed to describe the system under development, there are concepts
that support activities. Examples are (concepts used to express) guidelines, heuristics,
structure transformations, refinement and verification.
3.4 The Search for Concepts
The descriptions of individual methods and languages such as [CY91a, CY91b, C 94,
GR89, J 92, R 91, WM85] and [HP88] are textbooks meant to learn how a method works
and how it is applied. They do contain a treasure of information. Some information is on
the level of concepts. Books on methods describe guidelines and heuristics. Missing is
the history of the method, its design and evaluation. Methods are often well advertised
with their strengths, but not with their weaknesses and drawbacks. A designer of a new
method would like to know how existing methods were created, what the trade-offs
have been, and on what grounds design decisions have been made. This information is
often hard to retrieve. Partially this is due to the incremental historical development of
methods. Further, design decisions may have been taken in an ad hoc manner and are
not documented. Earlier scientific papers often only reveal a part of the backgrounds.
Most of the time they focus on certain specific topics in depth. They give limited concrete
help for the design of a method.
So far the issue was about knowledge and concepts in written material. This only yields
a small part of the required knowledge. In depth experience with a method is necessary
to be able to give a mature judgement about its merits and problems. We experienced
that it takes years to get skilled, even in a single specific method. Especially for the
evaluation of the heuristic part of a method experience is indispensable.
An in-depth study of concepts yields a profound understanding of methods and languages.
Having programmed in some object-oriented language, one may think to
understand concepts such as object, inheritance or aggregation. This understanding,
however, will often only be very shallow. A study of concepts shows that there is a
world of ideas and variations, but also confusion and disagreement or at least diverging