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Trade-Offs and Compromise


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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:

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 -

Stakeholder interests:

Sponsors Managers Developers End-Users Support
● 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
Functionality Tactical Strategic
Reliability Unessential Critical
Complexity Low High
Governance Minimal Critical
Documentation Unessential Critical

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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