Information Technology Reference
In-Depth Information
The ADo-oSS shown in Figure 13.5 involves the following steps:
a. Define FRs of the software system: The first step in designing a software system
is to determine the customer attributes in the customer domain that the software
system must satisfy. Then, the (FR) of the software in the functional domain
and constraints (Cs) are established to satisfy the customer needs.
b. Mapping between the domains and the independence of software functions:
The next step in axiomatic design is to map these FRs of the functional domain
into the physical domain by identifying the DPs. DPs are the “hows” of the
design that satisfy specific FRs. DPs must be chosen to be consistent with the
constraints.
c. Decomposition of
: The FRs, DPs, and PVs must
be decomposed until the design can be implemented without further decom-
position. These hierarchies of
FRs
,
DPs
, and
PVs
{
}
{
}
{
}
, and the corresponding
matrices represent the system architecture. The decomposition of these vectors
cannot be done by remaining in a single domain but can only be done through
zigzagging between domains.
d. Definition of modules—full-design matrix: One of the most important features
for the axiomatic design framework is the design matrix, which provides the
relationships between the FRs and the DPs. In the case of software, the design
matrix provides two important bases in creating software. One important basis
is that each element in the design matrix can be a method (or operation) in
terms of the object-oriented method. The other basis is that each row in the
design matrix represents a module to satisfy a specific FR when a given DP is
provided. The off-diagonal terms in the design matrix are important because the
sources of coupling are these off-diagonal terms. It is important to construct the
full-design matrix based on the leaf-level FR-DP-Aij to check for consistency
of decisions made during decomposition.
e. Identify objects, attributes, and operations: Because all DPs in the design hier-
archy are selected to satisfy FRs, it is relatively easy to identify the objects. The
leaf is the lowest level object in a given decomposition branch, but all leaf-level
objects may not be at the same level if they belong to different decomposition
branches. Once the objects are defined, the attributes (or data)—DPs—and op-
erations (or methods)—products of module times DPs—for the object should
be defined to construct the object model. This activity should use the full-design
matrix table. The full-design matrix with FRs and DPs can be translated into
the OOT structure, as shown in Figure 13.6.
f. Establish interfaces by showing the relationships between objects and oper-
ations: Most efforts are focused on this step in the object-oriented method
because the relationship is the key feature. The axiomatic design methodology
presented in this case study uses the off-diagonal element in the design matrix
as well as the diagonal elements at all levels. A design matrix element repre-
sents a link or association relationship between different FR branches that have
totally different behavior.
FRs
,
DPs
,
PVs
{
}
{
}
{
}
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