Information Technology Reference
In-Depth Information
Architects and designers
Figure 5.1
The level of detail.
When dealing with enterprise applications, having to build systems
using existing (sub)systems, even if one were to deal with specific tech-
nologies, is regarded as architecture. In case one were to build a new
component, one would be stepping into the realm of design — just as
the interface description would become design if you change the existing
implementation.
Quite often, the distinction between architecture and design is made
on the basis of the level of detail in the specification (Figure 5.1). The
architecture is considered a high-level description of the design. This is
fallacious because the content, and the purpose of an architectural spec-
ification, is very different from the design. To elaborate, in software, the
architectural document would discuss system and network topologies,
operational needs and goals, interfaces with other systems, and the justi-
fications for each. The design specifications would involve constraints of
programming languages, differences between two databases, and the
coding standards. The distinction is thus qualitative and not merely quan-
titative. Frances Paulisch differentiated these in terms of focus: while design
focuses on addressing the functional requirements of a system, an archi-
tecture covers both the functional and nonfunctional aspects (scalability,
performance, usability, etc.).
The difference can also be brought about by the implications of each
when DeMarco says that:
The absence of a thoughtful architectural act assures that there is
no initial accommodation to the changes that will propel the
product from version to version, or the change that allows the
essence of one product to be carried over into other members of
a product family.
Design focuses on a particular embodiment of the requirements in the
selected architecture.
