All projects try to gain control over these variables:
People and quality can be adjusted to conform to cost (typically people), scope (feature-set) and time. Cost, scope and time, however, are in direct conflict with each other. These three attributes are often shown as a trade off triangle:
In the above example you can only ever optimise one of the three - prioritising a low cost means reducing scope as well as time. If scope is large then both cost and time increase to compensate.
This principle applies in other areas too. Consider a system that must be usable, secure, and cheap. You cannot have all three - usability and security will cost you. A cheap system can be secure but not user friendly. And a user friendly system can be secure or cheap, but not both.
Software projects involve many people, from managers, developers, end-users and customers, for example, to testers and operations/support. Many have competing interests as shown here -
|● Quick schedule
● Low budget
|● No overruns
● No surprises
● Successful project
|● Interesting design work
● Exploration of new technical areas
● No grunt work
● Home life
|● Lots of features
● User-friendly software
● Fast software
● Robust software
|● No defects
● Good documentation
● Easily modifiable
Culture, the strategic nature of the project, reliability requirements, as well as complexity, governance and documentation requirements also demand consideration -
|Culture||Leading edge||Tried and tested|
A discussion of how these attributes might lead to a project management approach is here.
Many of these principles were developed by Barry Boehm and Rony Ross (see "Theory-W Software Project Management: Principles and Examples", IEEE Transactions on Software Engineering, July 1989).
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