Software Design Approaches
Software Engineering
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Notes
Top down Design
The principle underlying the design of a top-down software engineering system is the
proposition that every system is made up of several subsystems and that every
subsystem has components. and further, each of these subsystems or components may
have a series of subsystems or components, there will therefore be a hierarchical
arrangement of such sub-systems and components.
The top-down approach to designing involves the software system in its entirety and
then breaks it down to include more than one subsystem or component each having
specific turbo characteristics. To put it in less difficult terms, it makes a difference to
think of an motor, a component, or all of the components combined as a single
framework, and so on. .That is, each top level of a system is the most detailed as the
approach proceeds.
Top-down design enhances the efficiency for starting with a conceptual description of a
system and moving towards a more elaborated one. Once all the components are
instantiated the whole structure is functional as a system.
Top-down design is most effective when there is a requirement for anew software
installation and somehow there is no particular context, Task or requirements as
supported by the design process.
Design from the Bottom Up
When it comes to developing a new system by following a bottom-up methodology, the
preoccupation is with reworking or redesigning the system’s most advanced and
wanted, less complex components at the start. The model then (‘re-)’defines the more
detailed elements in as much depth as necessary to achieve the correct combination
with the elements of the next higher level. This decomposition occurs at every level until
the requested end system cannot be designated as one single component. The level
gets increasingly abstract as you go.
The bottom-up approach is more applicable and beneficial compared to a top-down
approach in cases where a new system is to be created based on an existing system,
equipped with a scope of overviews in which these most primitive elements within the
newer system structures can be explored and put to use.
Neither the Top-Down nor the Bottom-Up establishment of individual strategies in
methodologies is reasonable. In such cases, a more appropriate blend of the two
approaches is pursued by the developers.
