OUTSIDE THE BOX Forum: The Iron Triangle is Obsolete – Long Live the Scope Triangle, Part 1 of 2
The Scope Triangle is an interesting artifact of project management planning.
The term is not used in PMI’s PMBOK® Sixth Edition. The closest the PMBOK comes is to list scope, quality, schedule, budget, resources and risk as the constraints that impact the project. PMBOK goes on to say that these constraints form an interdependent set in that if one changes at least one other will be affected. In this 3-part article paper we will develop the Scope Triangle and show how it can be used in project management training.
Representing the Project
There are two ways to graphically envision the project that have been described in the literature. They are briefly described below.
The Iron Triangle
I cannot find the source for this term but it has come to mean the relationship between cost, time and scope (Figure 1). As is the case with the six constraints identified in PMBOK these three constraints also form an interdependent set. Specify any two and the third is determined. Or to put it another way if your manager says something like “I want you to develop a web-based order entry system for the new widget line and I will need it operational in 2 months. You have a budget of $50,000 to cover all one-time development costs,” you probably can’t do it. The chances that these three constraints form a consistent set are unlikely. Better would be “I need you to develop and order entry system for the new widget line and I need it operational in 2 months. How much will it cost to develop?”
Figure 1: The Iron Triangle
While Figure 1 may be an intuitive way to envision the project plan it has little value in project execution.
The Scope Triangle
The Scope Triangle (Figure 2) was first introduced in my training programs in the 1980s and subsequently published it in the first edition of my book “Effective Project Management: How to Plan, Manage, and Deliver Projects on Time and within Budget,” (Wysocki, Robert K, Robert Beck, Jr. and David B. Crane, 1995, New York, NY: John Wiley & Sons, Inc. ISBN 0-471-11521-5). The intention then was to illustrate with a simple graphic that the project plan was a system in balance, at least on day one of the project.
Figure 2: The Scope Triangle
The interpretation is rather intuitive, which is why there has been excellent instructional value in using it. The Scope and Quality are exactly bounded by the length of the three sides of the triangle representing cost, time and resource availability. Don’t try to draw the Scope Triangle. It is conceptual only. Given that the project plan makes sense on day one of the project the project plan is a system in balance. If any one of the five variables changes, at least one other variable must change in order to restore balance to the system. For example, if the client changes the due date of the deliverables to an earlier date, the length of the time side is reduced and the three sides no longer enclose Scope and Quality. To restore balance to the system anyone of several variables could change. For example, Scope could be reduced or the budget increased to hire outside contractors or some combination of the two.
Figure 2 is a useful way to envision the project plan and it has good value in maintaining the project plan, handling problem situations and managing scope change requests as is discussed below.
Using the Scope Triangle as a Management Tool
The Scope Triangle has been used in training programs for over 25 years. It is a good model in which to imbed and teach the following three project management activities.
Managing Scope Change
In the traditional approaches to project management a formal scope change process is needed. Most processes start with a request from the client. The appropriate team member will analyze the request and issue a Project Impact Statement in which alternatives and their impact on the project plan are documented. The client chooses one and the project plan is updated to reflect the chosen alternative.
The Scope Triangle is used to prioritize the alternatives from those that affect only the project team and the resources it controls to those that affect the resource managers to those that affect the client through added cost or schedule adjustments.
Problems are sure to arise in even the best planned projects. Schedule delays, supplier shipment errors, loss of a scarce resource and a variety of risks that materialize and must be handled. There is a hierarchy of resolutions (related to the Scope Triangle) that are offered in the order listed:
- Accommodated within project resources and timelines
- Accommodated but will require extension of deliverable schedule
- Accommodated within the current deliverable schedule but additional resources will be needed
- Accommodated but additional resources and extension of deliverable schedule will be needed
- Accommodated with multiple releases and prioritization of deliverables across release dates
- Cannot be accommodated without significant change to the project
Representing the Project Portfolio
Recent application of the Scope Triangle deal with some basic concepts of project portfolio management especially agile portfolio management. In the Scope Triangle shown in Figure 2 replace the inside of the triangle with all of the projects vying for inclusion in the portfolio. The initial proposed projects will most likely require more time, or money or more human resources available at that time.
Figure 3: Project Portfolio Management
Think of removing the proposed projects in some reversed prioritized order until each of the three bounding constraints are all met. The prioritized order will be based on some combination of risk and business value.
Putting It All Together
The Scope Triangle is a valuable tool for teaching scope management, problem resolution and portfolio management concepts. It is an intuitive graphic that every project manager should burn into their brain to help them approach the three applications with a much better strategy.