STRATEGY OF DESIGN

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STRATEGY OF DESIGN

Strategy design techniques helps the developers to deal with the size and complexity of a program.

Analysts create instructions for developers about how the code should be written and a piece of code should be fit together to form a program.

It is important for two categories:

Event pre-existing code,if any,needed to be understood and pieced together.

It is still common for a project team to write some code and produce original programs that support the application logic of the s/m.

There are many strategies or techniques for performing s/m design.They include:

BOTTOM-UP APPROACH

TOP-DOWN APPROACH

HYBRID APPROACH

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BOTTOM UP APPROACH

Bottom up processing is an approach where there is a progression from individual to the whole.

This model starts with the most specific and basic components.

It proceeds with composing higher level of components until the desired s/m is not evolved as one single component.

With each higher level the amount of abstraction is measured.

Bottom up strategy is more suitable when a s/m needs to be created from an existing s/m and the basic primitive can be used in the newer s/m.

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TOP DOWN APPROACH

Top down approach starts with a big picture.

It breaks down from there into smaller segments.

This approach is the piecing together of a s/m to give rise to more complex systems.

Thus making the original s/m subsystem of the emergent s/m.

Each and every s/m is composed of more than one subsystem and it contains no. of components.

Further,those subsystems and components may have their own set of subsystems and components and create a hierarchical structure of the s/m.

This design takes the whole s/w s/m as a one entity and decomposes it to achieve more than one subsystem and components based on some characteristics.

Each subsystem and components is then treated as a system and decomposed further.

This process keeps on running until the lowest level of s/m in top down hierarchy is achieved.

Top down design starts with a generalized model of the s/m and keeps on defining the most specific parts of it.

When all components are composed,the whole s/m comes into existence.

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HYBRID DESIGN APPROACH

Pure bottom up or top down approaches are often not practical.

For a bottom up approach to be successful we must have a good notation of the top to which the design should be heading.

Without a proper idea about the operations needed at higher level,it is difficult to determine what operations the current layer should support.

For top down approach to be effective we must have some bottom up approach for the following reasons:

To permit common sub modules.

Near the bottom of the hierarchy,where the intuition is simpler and the need for bottom up testing is greater.

In the use of pre written language modules,in particular reuse of modules.