Answer to Question 1
The systems development life cycle (SDLC) process is falling out of favor in the
systems development community, primarily for two reasons. First, the nature of the SDLC denies
what every experienced developer knows is true: systems requirements are fuzzy and always
changing. They change because they need to be corrected, or more is known, or users, once they
see a part of the application, change their minds. Other reasons are that business needs change, or
technology offers other possibilities. According to the SDLC, however, progress goes in a linear
sequence from requirements to design to implementation. Sometimes this is called the waterfall
method because the assumption is that once a phase is finished, it is not revisited. Requirements
are done. Then design is taken up. Design is completed, and is followed by implementation.
However, experience has shown that it just doesn't work that way.
The second reason that the SDLC is falling out of favor is that it is very risky. The people for
whom the system is being constructed cannot see what they have until the end. At that point, if
something is wrong, all the money and time has already been spent. Furthermore, what if the
project runs out of money or time before it is completed? The result is a form of management
blackmail in which the developers ask for more money or time. If management declines, which it
might because the time or money at that point is sunk, they are left not only with the loss but also
with the unmet need that caused them to start the process in the first place.
Answer to Question 2
A market-basket analysis is a data mining technique for determining sales patterns. A
market-basket analysis shows the products that customers tend to buy together. This gives
companies an opportunity to cross-sell.
Life
Phosphorus cycle in a lake ecosystem.
O2 Cycle
Menstrual cycle
Systems of humans
Drug elimination: half-life to steady state.