Schedules are probably what you immediately think of when the term Project Management comes up. Although a project schedule is not the only concern of a project manager, it is certainly one of the most visible aspects of a project. From the child who wants to know “are we there yet?” to the sales team wondering if the new toy will be on the shelves in time for the Christmas market, stakeholders’ impressions of the project’s success are often coloured by whether or not the project is delivered in the expected timeframe.
On this page:
- Sequence Activities: Identifying Dependencies and Work Breakdown
- Estimating Resources and Durations
- Developing the Schedule and Critical Path Analysis
- Tracking Progress and Controlling the Schedule
- In Summary
Sequence Activities: Identifying Dependencies and Work Breakdown
For a Project Manager, scheduling begins with a plan. It is always useful to write down how, exactly, you are going to create and track the schedule. Once the Project Sponsor and the key stakeholders agree that this is the way to go, the Project Manager will take the scope definition for the project (carefully developed using Project Scope Management techniques) and refine the Work Packages defined during that effort into tasks, or what the Project Management Institute calls Schedule Activities.
Scope management is concerned with breaking down the work into chunks – called Work Packages – that can be assigned to individuals, or even organizations. A builder might define a Work Package called “Paint House”. A painter, receiving this assignment, will need to determine how much paint is needed, carry out remedial plasterwork, purchase paint and then apply undercoats and topcoats. Breaking the work packages into individual tasks is part of the Define Activities project management process. It is a really useful exercise, because you are explicitly stating what work is needed to develop a particular part of the ultimate deliverable.
Estimating Resources and Durations
Once the tasks (or Schedule Activities) have been defined, they need to be put in order. This is the Sequence Activities process. The important thing here is to order the tasks as if you had infinite resources available to carry them out. The concern at this stage is to identify the unavoidable dependencies between the activities. An obvious one in the painting example is that the undercoat has to go on before the topcoat. Also, the painter cannot go to work before the house is actually built! Similar logic dictates that the paint has to be purchased before it can be applied and the paint cannot be purchased until we know how much is needed.
However, if we have to paint ten rooms, there is nothing to stop us painting them all at the same time – if we had ten painters. This is why the initial network diagram, showing the dependencies between tasks, should not consider resource constraints. If the stakeholders want the project finished earlier, we will know where we can add extra resources and carry out tasks in parallel.
Developing the Schedule and Critical Path Analysis
Having ignored resource constraints for the Sequence Activities work, we need to come back down to earth now and start estimating what resources – people, equipment, materials – we need to carry out these tasks and how long we expect the work to last.
If we have done similar work before, we can base our estimates on experience. However, even if we have done this sort of thing previously, we might have had different experiences. For instance, in one situation, the painters might have finished the job in two days, whereas in another house it took four days.
The Project Manager needs to assess the range of estimates and decide on a most likely value. Essentially, the lowest estimate (what is called the optimistic one) represents the situation where all goes well. Higher estimates reflect risks to the project. It is best practice for a Project Manager to adopt the optimistic estimate, but to add contingency reserves to the schedule to take account of risk. In this way, contingency is explicit and not padded into the estimates.
While estimation is most often associated with durations, the Estimate Activity Resources process involves similar analysis. Note that the sixth edition of the PMBOK® Guide has moved the Estimate Activity Resources to the Project Resource Management knowledge area. Fortunately, estimating materials is generally easier – if you have to tile a 5m2 wall and each tile is 10cm2, then you can make a very accurate estimate. However, you should add a bit extra to allow for breakages. This again is a contingency reserve.
Having concluded the Estimate Activity Resources and Estimate Activity Durations processes, it is now time to develop the schedule. This involves taking the network diagram we drew in the Sequence Activities process and adding the duration estimates to the tasks. We also need to revise the topography to reflect the resources available. Some of our parallel activities will have to be done in series now. In other words, we need to introduce resource constraints into the picture.
Tracking Progress and Controlling the Schedule
To determine the Critical Path (i.e. the longest sequence of Schedule Activities), we need to carry out a Forward Pass and then a Backward Pass through the network diagram. This will tell us what the finish date of the schedule is. If we discover that we will finish later than required – e.g. we will miss the Christmas market or the important trade show – we can look at adding more resources in order to get work done in parallel or we can look at fast tracking – starting tasks before their predecessors are fully finished. Once the schedule is acceptable, we need to archive this version as the initial baseline. As we carry out the work, we will need to compare the actual times taken to carry out tasks and the number of resources actually consumed with our plan.
If our estimates are good, tracking the project’s progress is easy. However, we might notice that all our estimates are either too small or too big. We might have to re-baseline the schedule to reflect this trend. More seriously, we might find the schedule thrown off track because one task takes way longer to complete than estimated. This can happen if a risk materializes for instance. Another problem for the schedule is if a stakeholder makes a change request. Adding extra work to the project can push out the schedule, so this needs to be considered before approving the change.
Project Managers can report on schedule progress by using Earned Value Management and maintaining Schedule Variance and Schedule Performance Index values. Reporting progress, adapting the schedule to reflect changing circumstances and taking necessary corrective and preventative actions are all part and parcel of the Control Schedule process.
A building is only as strong as its foundation. Unless the scope is defined correctly and the estimates are based on sensible analysis – e.g. previous experience, industry norms – there is no benefit in controlling the schedule tightly. Instead of worrying about variances between planned and actual, every effort should be made to record the actual values and make them available to future projects. As actual figures are reported, it might even be possible to adjust this schedule to reflect our new knowledge.