How you anticipate and react to these changes means the difference between project success and failure. The trick is to adeptly deal with two potential wild cards throughout the project life cycle: constraints and assumptions.
Constraints
Constraints are any element that may restrict, limit, or place control over a project, project team, or project action. Constraints impact projects by dictating the limits or approaches that the project team may pursue. You must consider these elements when defining project tasks, budgets, schedules, personnel, technology, and so on.
At the beginning of each project, make a complete list of constraints that will impact the project. Then, you must include these items in formal project initiation, planning, and execution documents, beginning with the project charter. As the project progresses, you'll probably need to go back and add or modify this list.
Assumptions
Assumptions are circumstances, conditions, or actions that you may believe are true--even without factual support. You may find yourself making assumptions about such topics as the applicability of licensures, the impact of environmental changes on project tasks, resource availability, and vendor schedules.
It's important to note assumptions can be a significant source of project risk. Therefore, you should formally record assumptions beginning in the project charter and throughout later project documents.
The difference between constraints and assumptions
It's possible to explicitly identify constraints, whereas assumptions require research for verification. You'll find yourself spending a significant amount of time chasing down details for assumptions that are considered substantive to a project's success. You should at least put assumptions through the common "What if/Then" analysis process. This technique asks the question, "What will the impact be if the assumption is proven to be false?" This information is then fed to risk management activities. The "What if/Then" analysis also helps to prioritise which assumptions may have the greatest impact on your project.
A common mistake many project managers make is to assume that the importance or validity of a constraint or assumption remains constant throughout the project life cycle. This is almost always incorrect. Instead, constraints and assumptions change dynamically in response to changes in the project, environment, and organisation. For this reason, it's crucial that you're diligent about tracking and evaluating assumptions and constraints routinely throughout the project.
