first: 2011-10-12 last: 2011-11-10

The title of this subsection is taken from Henrik Gedenryd's thesis on his cognition oriented analysis of design activities. [Gedenryd 1998] His analysis will be recognized by most people who are, or have been, involved in design processes.
He positions a practical approach against the traditional, intellectual, what he calls \emph{intra-mental} approach. With intra-mental cognition he indicated the view of cognition as a process that is contained entirely within the mind, and which is performed by the mind alone, cognition being strictly isolated and separated from action, perception, and every aspect of the surrounding world, be it material, social or cultural. [id.: 7-8]
Information Processing Theory proved to be inadequate as a fundamental theory of cognition. The standard diagnosis is that its problems are located in the computer model of the mind and the symbolic view of cognition. According to Gedenryd this is not the crucial defect. Intra mentality is the culprit that caused the problems in explaining cognitive processes. One of the reasons that this key issue has not been recognized is the fact that it is not stated explicitly. [id.: 9]
In contrast to the intellectual perspective, there is an alternative approach where cognition is seen as fundamentally practical by nature. He then refers to Husserl, Heidegger and pragmatism, in particular as worked out by John Dewey. [id.: 10]

How designers don't work

In Practical Reasoning and Engineering Jesse Hughes reviews some more or less formalized concepts.

Engineering is successful to the extent that it provides means to satisfy our needs and desires, i.e. if it is successful as a method of practical reasoning. The final end of the design process is the technical artifact. Artifacts - both types and tokens - are evaluated in terms of their effectiveness and reliability, that is in terms of their efficacy as means. [Hughes2009: 375]

He argues that instrumentalism is eminently applicable as a theory of practical reasoning in the process of engineering design. (id.: 376)
The fundamental thesis of instrumentalism is that practical reasoning consists of nothing but \emph{means end} (short for \emph{means to an end}) reasoning.
Hughes then refers to the more formalized methodologies as for example described in Dym and Little. In his section \emph{Syllogism and means} a formal structure is specified of a means end reasoning as found in (Curchland, 1970):

> I want φ
> Doing α is a way for me to bring about φ under these circumstances.
> There is no other way to bring about φ now which is preferable to me than doing         α.
There is no sufficient reason for me not to bring about φ under these circumstances.
Therefore, let me do α

However, designers do not work according to such strict logical schemes! In his chapters The master plan and The failure of design methods of his thesis Gedenryd gives a critical analysis of design methodologies because the conventional theories describe the wrong concepts. He considers these as belonging to the same family of rationalities as described by Pappus way back in Alexandria in the fourth century. Pappus described a method, in the domain of mathematics, of how to analyze a new theorem first down to basic axioms in order to use the same steps to synthesize the theorem by building up steps from axioms. G.Polya in his How to Solve It refers to Pappus' concepts as a general method to solve problems and to create solutions. Since the middle of the last century, this methodological concept has been generally adopted and has been worked out in various ways. These design methods have been applied on large scale by NASA and military-type technology projects. This model became also well accepted in the area of software engineering.

Gedenryd refers to several authors who reject these methodological concepts as these would only be applicable to simple routine design work. [Gedenryd 1998: 59-62) He states that the fundamental mistake, made by Pappus first, and consequently made by all who worked out the concept into design methodologies, is that the method describes the products, not the processes. [id.: 62]

Also Bryan Lawson, in \emph{How Designers Think, the design process demystified}, evaluates various design methods and design process maps". [Lawson 1980: 33)] The common idea behind these methods and maps is the assumption of a sequence of distinct and identifiable activities can be applied. He concludes that: Unfortunately these assumptions turn out to be rash.

How designers work

The start of a design as an action to solve a problem, has been criticized by many as Gedenryd emphasized with a couple of references. Donald Sch\pol on coined the term \emph{problem setting} to indicate that the identification of a problem as a first step should not be seen independent from the solution. Or put more sharply, designers create problems first.

In Educating the Reflective Practitioner Donald A Schön made a distinction between technological activities in activities on the high grounds and between activities in the swamps.\fn{Donald Schön studied philosophy, Ph D on John Dewey's theory of inquiry, wrote with the experience of a working life as an industrial consultant, technology manager and teacher in a professional school. [Schoen 1983:vii) The activities on the high grounds can be handled" by the book. The activities in the swamps are the more complex, unique ones, where various elements, not all fully known, play a role and judgment based on considerations of various aspects including economics and risks is required. [Schön 1988a: 8) He worked in a team that observed and trained professionals in design. Based on their observations they recognised that inherent, in the practice of unusually competent professionals lies a core of artistry.

[This] artistry is an exercise of intelligence, a kind of knowing, though different in crucial respects from our standard model of professional knowledge. It is not inherently mysterious; it is rigorous in its own terms; and we can learn a great deal about it by carefully studying the performance of unusually competent performers.

Some different competences were observed:

There are an art of problem framing, an art of implementation, and an art of improvisation, all necessary to mediate the use in practice of applied science and technique. [Schön 1988a: 13]

Teachers say:

that there are essential covert things" that can never be explained either the students gets them in the doing, or he does not get them at all. [id.: 82]

Schön reported that they analyzed the characteristics of the architectural design, but claimed these characteristics to be equally applicable in other areas.

The designers were asked to give as much explanation as possible of what they were thinking, considering and doing. Sketches were collected and the sessions were taped. Although the design processes and considerations were quite different a number, of more or less common elements could be detected.

All the participants reasoned their way from premises to conclusions. Their premises took the form of design rules, sometimes explicitly stated, more often implicitly understood; their conclusions took the form of judgments about the desirable or undesirable directions of designing or decisions about design moves. Rules were used but never in an absolute way, exceptions were easily made.

Especially references and experienced archetypes guide the selection of rules, but they are also base for the challenging of the rules. Functional types, used to provide information necessary for the application of design rules, supply the intermediate premises of reasoning.

Schön  opposed the instrumental model as a structured way of designing. Instead, he claimed design should be seen as a kind of art. With examples from workshops he argued that the art can improve by experience, by being coached, but not without a certain amount of talent, to be there as a starting predisposition. [Schoen 1988a: 80-99]

System Design

The reference model defined in section 3.3. is based on the redesigning of existing functional artifacts. System design does not always start with one or more specific examples, but with a System Requirements Specification (SRS) for new applications.

The design of larger systems in general will show a combination of what usually is indicated as top-down and bottom-up design processes. The top-down approach starts with a split of required functions into subfunctions. During this split, system designers already have a notion of the kind of subsystems and components that will be available or are feasible to be realized. Subfunctions in general will have a coherent functional structure with welldefined, (or definable during the later phases) interfaces. That does not necessarily mean they are closed physical units. For instance, complex subsystem functions in general are to be considered as a conglomerate of sub functions.
These subfunction can be allocated as welldefined spatial units, but more often the function is distributed over the complete system.

For instance, the brake system of a car should from a functional design point of view realize the brake function. However, the requirements specification is related to the overall specification of the car. The design specification is related to other characteristics of the car and should specify the allocation of functional requirements to user interfaces and the the brake controls, the servo unit, the control indicators, the hydraulic system etc). Each of these subfunctions should be mechanically positioned.

System design also requires some kinds of basic capabilities to have an overview of complexity and a tacit knowledge of the functions and additional characteristics of system modules.

Philosophygarden        of Hans Tromp
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