There is no Iron Triangle in Project Management. In PM we learn the holy trinity of the triple constraint, the concept that we are operating within borders, and that those borders are interdependent. Oh yeah, and “triple” or “triangle” indicates that there are three. Although the image is powerful to instruct, it is plain false. There are more than three types of constraints. Environmental, law, physical to name just a few in addition to things like time and money.
Photography by Jef Poskanzer.
The job of a Project Manager is to guide a project towards the desired goal respecting those borders. The difficulty lies in the fact that this is always a trade off. If more has to be created, you either need more time or more money. Both increase the cost. Or if we paint the wall blue this week, the same people cannot spent their time on fixing the sink. Project Management is a profession of trade offs and decisions.
Tom Gilb and Mark Maier present in their paper “Managing Priorities: A Key To Systematic Decision Making” a solid foundation on how this could be done.
In their view every requirement to product or process of the project can be expressed within some kind of metric. As a value on a natural or constructed scale.
“All the requirement types can be specified simultaneously as target levels (levels we aim to get to) and constraint levels (levels we are warned to avoid). As a simple analogy, consider room temperature: we aim for just right, and avoid too hot or too cold.”
“A constraint is a specification that should be met, otherwise certain definable negative consequences will follow. Constraints cannot be absolute, because the cost of respecting the constraint can exceed the negative consequence in the overall value schemes of the authoritative stakeholders.”
By placing all requirements in the same league, priorities can be assigned to all aspects without getting the idea of comparing lemons and oranges.
“Priority is relative right of a requirement to the utilization of limited (or scarce) resources.”
It will guide the Project Manager and the authorized stakeholders in making decisions how to allocate to resources. A desired goal is needed for a project to ultimately judge trade offs against.
The paper provides a clear linkage between requirements, constraints, priorities and the allocation of scarce resources.
What more does a PM want?
8 Comments
Also a good pointer on this subject:
http://crossderry.wordpress.com/2008/06/23/more-on-the-triple-constraint/
Thanks for this article.
Ranjit Biswas and I have written extensively about this – and it will be an entire chapter of our upcoming book, The Fiddler on the Project.
In the meantime, read posts at http://scopecrepe.blogspot.com
Thanks for the comment Rich. Looking forward to the book. In anticipation we’ll read your great blog
bas,
As the poster in your first reference says “constraints are NOT indepedent from each other.” You may be interpretating the triple constraint wrongly. I see your point about more than three.
Here in space and defense the three are Cost, Schedule and Techncial Performance. TP captures ALL the dependent and i ndependent variables, quality, requirements, etc. Eveythhing that is not cost or schedule.
If there is a change in the requirements (the technical performance measures), and if there is a change in the cost and/or the duration to deliver this new change – then there is a casual connection between cost, schedule, and techncial performance. If there is no causcal connection, then there there is no triangle.
The determiniation of these causal connections of the domain of the “triangle.”
I know of no non-trival project requirement where thre is not a causal connection between cost, schedule, and technical performance. Hence the “triangle” of dependent variables.
Once this casual connection is made, ONLY THEN can the tradeoffs Tom speaks of be made. Prioritization, seqeuncing, resource allocation and other “adjustments” to the project plan can be made. These decisions are based on knowing what impacts there are on the other Dependent variables of the triangle.
This is the basis of portfolio management, programmatic risk analysis, and schedule optimizaiton – probablistic critical paths.
So if you roll up the collection of depedent variables into classes of Cost, Schedule and Not-cost&schedule you get three – a triangle.
This notion that quality of the third leg is obsolete and no longer valid in any modern defense or space project. Thanks for the great post.
Glen B. Alleman
VP, Program Planning and Controls
Aerospace and Defense
Lewis & Fowler
Denver, Colorado
Hi Glen, thanks for the insightful comment… I really have to think about this one
Cheers, Bas
Project Managers exist to drive down programming costs and whip programmers to deliver faster because CEOs get tired of doing it.
The primary benefit of outsourcing is that whipping empolyees oversees and sweat shops are more acceptaed then in the USA.
That is it. End of story.
wow alex… there seems a lot of whipping going on in your part of the world… sorry to hear.
But believe me, there are also companies where this is not end of story.
Take care! Hope you find your dream employer soon.
The link to the Gilb article doesn't seem to work. Goto the Gilb site: http://www.gilb.com/tiki-list_file_gallery.php?...
Scroll down or search the page for “Managing Priorities”, you can download from there… lots of other good stuff there to
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