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Iterative/Incremental Development -I
JavaFAQ Home » Java Notes by Fred Swartz
There are many ways to divide the Software Development Life Cycle.
I've choosen some common terms, but don't be surprised to see other terms.
Here's a brief explanation of the what each means.
- Analysis - Also called requirements analysis. This is the process
of figuring out what the customer wants or needs.
- Design - This is the process of deciding how to structure the
program. For large projects this is often divided into two stages:
architectural design and detailed design.
- Testing - This is the process of trying to detect errors in the program.
For large programs this is typically divided into two parts: unit testing
tests individual modules and integration testing sees if the total
program works when all the modules are run together.
Waterfall technique -- traditional, but risky
When you understand a problem and its solution very well, it's possible write a
program by following the steps at the left. But problems are rarely understood
as well at initially thought, and this "waterfall" approach has turned out to be
responsible for an
high number of software project failures. There are several reasons for this.
This are some of the typical reasons that use of the Waterfall methodology is
not recommended. An iterative/incremental approach is better.
- Mistakes in the understanding the the early phases (eg, requirements
analysis and design) that are not discovered until the testing or
integration phases are expensive (ie, time consuming) to fix, costing much
more time (eg 20x) to fix than if they had been done right the first time.
The earlier mistakes are discovered, the easier they are to fix. The cost of
finding an error that must be fixed in the completed design or coding phases
is usually quite high. Student programs often suffer from this in several
- The requirements of a programming problem may not be well
understood. For example, the instructor may not have written a clear
- If the student is designing their own project, they may not always
be clear about what they want. Typically, the idea for a student project
evolves as the project progresses.
- Sometimes the programming solution may not be well understood, and a
plan is made based on incorrect ideas about what will work.
- The resources (ie, time) required to complete a program are not
accurately estimated (almost always in the optimistic direction). In
commercial development this results in late delivery and cost overruns or
cancellation. In student programs it means that the program doesn't run,
with unhappy consequences.
Disadvantages compared to iterative method
- The cycle of getting rid of compilation errors can be unnecessarily
- The output may not be what you want, but when debugging an entire
program, it's harder to identify the source of the error.
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