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Introduction
[There are no right or wrong answers to the first four exercises, which are intended to
give you some feedback on the background of the students and to get them thinking
about the value of using a software design methodology.]
1.1
The amount of time spent on analysis, design, coding, and testing/debugging/fixing de-
pends on the methodology used. Using an OO approach, we find that our effort is split
approximately 20% on analysis, 30% on design, 40% on coding, and 10% on testing/
debugging/fixing problems. The exact split depends on factors such as the type of sys-
tem and the amount of experience with similar systems. We have found that paying extra
attention to analysis and design cuts the total development time. It is a lot easier to avoid
a problem during analysis and design than it is to find and fix it later on.
One of the most difficult areas of project management is estimating how much effort
a project will require. One method that we use is to break the total effort down into sev-
eral tasks. We think about each task separately and estimate how much effort is required,
based on our experience with similar tasks.
One major problem that we have encountered is underestimating the time and effort
required to complete a project. Most software projects are finished late and over budget.
We try to deal with this by carefully considering our estimates and explicitly allowing
for contingencies.
Premature implementation is another problem. Because of an anxiety to complete a
project, developers sometimes substitute implementation for design, resulting in sys-
tems that are hard to debug. The resulting software suffers from unwarranted assump-
tions and fuzzy thinking. With such an approach, developers bog down in details and
find it difficult to see flaws.
In one of our projects we quickly prototyped a trivial master-slave communications
system. We did the initial coding in a week without benefit of a thoughtful design. The
resulting system crashed due to occasional data communications errors. We applied
many patches to the system over a period of three months. Each time we thought we un-
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