AXIOMATIC DESIGN IN SOFTWARE DESIGN FOR SIX SIGMA (DFSS) - Software Design for Six-Sigma: A Roadmap for Excellence - page 338

mapping mapping mapping mapping

FRs
.
.

FRs
.
.

FRs
.
.

FRs
.
.

DPs DPs DPs DPs

. . . . .

.
.

.
.
.

.
.
.

.
.
.

Level 1 Level 1 Level 1 Level 1

What What What What How How How How

Zigzagging Zigzagging Zigzagging

Process

Zigzagging
Process

Level 1.1 Level 1.1 Level 1.1 Level 1.1

.
.
.

.
.
.

.
.
.

.
.
.

.
.
.

.
.
.

.
.
.

.
.
.

What What What What How How How How

FIGURE 13.4 The zigzagging process.

this software, and the system representation for software holds at every hierarchical
level.
The importance of the design mapping has many perspectives. Chief among them
is the identification of coupling among the functional requirements, which result
from the physical mapping process with the design parameters, in the codomain.
Knowledge of coupling is important because it provides the design team clues with
which to find solutions, make adjustments or design changes in proper sequence, and
maintain their effects over the long term with minimal negative consequences.
The design matrices are obtained in a hierarchy and result from employment
of the zigzagging method of mapping, as depicted in Figure 13.4 (Suh, 1990). The
zigzagging process requires a solution-neutral environment, where the DPs are chosen
after the FRs are defined and not vice versa. When the FRs are defined, we have to
zig to the physical domain, and after proper DPs selection, we have to zag back
to the functional domain for further decomposition or cascading, though at a lower
hierarchical level. This process is in contrast with the traditional cascading processes
that use only one domain at a time, treating the design as the sum of functions or the
sum of parts.
At lower levels of hierarchy, entries of design matrices can be obtained mathe-
matically from basic physical and engineering quantities enabling the definition and
detailing of transfer functions, an operational vulnerability treatment vehicle. In some
cases, these relationships are not readily available, and some effort needs to be paid
to obtain them empirically or via modeling.

AXIOM 1 IN SOFTWARE DFSS 5

13.3

Several design methodologies for software systems have been proposed in the past.
Two decades ago, structured methods, such as structured design and structured

5 See and 2000.