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SearchDatabase.com's Database Developer
June 20, 2001
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Welcome to the searchDatabase.com Database Developer newsletter!
Today's tip, "The database development life cycle" can also be viewed
online at:

http://www.searchDatabase.com/tip/1,289483,sid13_gci750181,00.html

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"The database development life cycle"

By Mike Blaha

To ensure extensible, flexible and fast applications, database
developers should heed tried-and-true software engineering
principles.   The typical stages of database application
development--and indeed all types of development--include analysis,
design, implementation, data conversion, testing, training, and
maintenance.  This article from InformIT discusses four common
approaches:

Waterfall 
---------

The classic life cycle paradigm is the waterfall approach. Developers
perform the software development stages in a rigid linear sequence
with no backtracking with this approach.

The waterfall approach is suitable for well-understood applications
with predictable outputs from analysis and design. It is also used in
many contractual situations, especially for government projects
(regardless of its suitability).

A waterfall is inappropriate for applications with substantial
uncertainty in the requirements, which is true for most applications
you will encounter. Too many organizations attempt to follow a
waterfall when requirements are fluid. This leads to the familiar
situation in which developers complain about changing requirements,
and the business complains about an inflexible information systems
(IS) organization. A waterfall approach also does not deliver a
useful system until completion, which makes it difficult to assess
progress and correct a project that has gone awry.

Summary:

   Strengths - Suitable for applications with predictable outputs.

   Weaknesses - Copes poorly with fluid requirements. Does not
deliver a system until completion.

Rapid Prototyping 
-----------------

With this approach, you quickly develop a portion of the software,
use it, and evaluate it. You then incorporate what you learned and
then repeat the cycle. Eventually, you deliver the final prototype as
the finished application, or switch to another approach after a few
prototypes. You must quickly cycle through prototypes (typically, an
iteration every two or three months) for this approach to succeed.
Rapid prototyping focuses on the input of user interviews; if you can
glean information from other input sources, you can reduce the number
of prototypes.

Rapid prototyping promotes communication. You learn about the needs
of the customer, and the customer learns what automation can provide.
Thus, prototyping targets a core difficulty of software
development--finding the true requirements. Rapid prototyping
provides frequent checkpoints for assuring customers that development
is going well. It also lets developers experiment with troublesome
aspects of design and implementation. They can test a difficult
algorithm, and find whether it works well before committing to a full
implementation.

The prototype may be throwaway, or it may be gradually elaborated
until you achieve a working system. This is the weakness of rapid
prototyping: Often a prototype is unsuitable for enhancement, but you
may receive business pressures to enhance it, nonetheless. The key to
success is to be prepared to discard early prototypes. Prototypes
should be enhanced only if they are successful in the field and have
a robust architecture.

Summary:

   Strengths - Elicits requirements. Provides milestones. Lets you
experiment with troublesome issues.

   Weaknesses - There may be business pressures to extend a fragile
prototype. Must throw away code.

Click here for the remainder of the article, including a discussion
of the two other development approaches--incremental and 4GL:

http://www.searchDatabase.com/tip/1,289483,sid13_gci750181,00.html


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