Requirements Risk
The Auditor General of Canada, Sheila Fraser, released a
report on Tuesday that in part examined the purchase of
15 Boeing Chinook helicopters.
|
all-in cost |
delivery date |
| 2006 |
$2.0 billion |
2008 |
| yesterday |
$4.9 billion |
expected 2013 |
After the contract was awarded in 2006:
From that moment on, National Defense then spent three
years actually defining the requirements, and three years
later in 2009, came out with requirements and contract
for a helicopter that was very different, totally
different, a helicopter that had never flown before,
as compared to the one that they had put out in the
advance contract award notice.
—Shiela Fraser, CBC interview
Iterative and Incremental Development
Iterative and incremental development is a development
process characterized by two features. The first is iteration,
meaning the process goes through repeated cycles. The second is
incremental, meaning more functionality is added as iterations
occur.
Iteration
The figure shows one complete cycle as a waterfall model,
but it is common to skip steps in a cycle.
Iteration makes it possible to identify mistakes so that they
can be corrected for the next iteration. Also, modifications
can be added in the next iteration.
Incremental
Gradually adding new features over iterations allows for
incremental growth of the software system. Each incremental
release can be given to the customer to evaluate.
Buzzwords
Iterative incremental development is currently very
popular. Many frameworks rely on these ideas:
- Rational Unified Process
- Extreme Programming
- Agile development
UML Class Diagrams
The Unified Modelling Language (UML) is used to
specify, visualize, and document object-oriented systems.
The UML class diagram describes the structure of a
software system by showing the classes used in the
system, details of the classes (their attributes and
methods), and the relationships between the classes.
Class Diagrams I
Very early in the development process it is
likely known that a class is needed, but its
functionality is largely unknown. In this
case, we can use a class diagram containing
just the name of the class.
Class Diagrams II
Once more is known about how the class will be
used, more details (such as the public
attributes) can be added to the class diagram.
Class Diagrams III
When the class needs to be implemented, more features
of the class will emerge, such as what methods are
required.
Relationships Between Classes
Test 5
Written part will cover regular expressions of
simple to very modest complexity. A link will be given
to the Pattern documentation.
