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Ep17: The Iron Triangle

Today, let me cover the Iron Triangle.

Developed by Dr Barnes in '69, the Triangle is a model of the constraints of project management. The original triangle follows a waterfall approach: Scope is fixed and Resources and Time are variable.

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Scope is work to be done, such as features & functionalities, to deliver a working product.

Resources include budget and team members working to deliver and execute.

Time, or Schedule is when teams deliver to the market, such as releases and milestones.

The purpose of the Iron Triangle is to give teams the necessary information to make business trade-offs.

E.g. If Scope is fixed and you're facing delays, you can add more people (Resources), or change the schedule (Time). Changes in one constraint necessitate changes in others to compensate, or quality will suffer.

Unlike waterfall development, Agile projects have a fixed Schedule (Sprints) and ideally fixed Resources while the Scope varies. (Teams gain efficiency through trust & continuity, so best to keep them consistent).

Agile focuses on high-level requirements rather than going deep and detailed upfront. The Scope of a project (Backlog) gets frequently managed and groomed (prioritised) in Backlog Refinement and Sprint Planning.

I first posted this article here, and used information from


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