Some people ask why IPM insists that project work be broken down into small units. This questioning assumes that it is easy to look at a work package and say "we know how to do that." This idea can be very wrong. Those who look at a large work package with the confidence that they (or their work group) know all there is to know about doing the job, assume that the package can be broken down into smaller units as they go along. They think that when they start the first tasks, the subsequent tasks will become obvious. However, all projects have some unique characteristics, and therefore, some hidden traps and bottlenecks when approached at only the major task or work package levels. Breaking down the package into tasks and subtasks is an exercise in discovering if "we" really know how to do it. A project manager might assume, for example, that a software package output could be directly input into the next task user's equipment. Careful task breakdown may reveal that a conversion step is necessary before Task Number 1's output can be used with Task Number 2's equipment. However, more important is the real possibility that the work package team will unexpectedly reach a hurdle that they have not considered, one that cannot be surmounted without significant outside help.
Another reason for work breakdown is connected to the projected completion date for the project. The task time estimates, which are provided by work package leaders and add up to the project completion date, are always less accurate than those derived by adding the time estimates from the series of smaller tasks that comprise the work package.
The initial analysis provides the base information for the project's planning time buffer analysis. When the initial analysis and project plan are completed, the project manager will lead the team through the process of determining the appropriate time buffers, or "risk tasks," for the plan. The initial analysis, with these risk tasks added at strategic places, along the flow of project tasks, provides a finish date that can be used with confidence.
The breakdown process also may suggest that several trials may be necessary before reaching satisfactory task completion in some task areas. Information may surface that suggests two or more parallel work teams are needed to assure the timely completion of certain tasks. This is valuable data to keep for the Gantt chart.