Schedule development is the process that enables the project manager to take the time estimates derived in the activity resource and use them to create the project schedule. The project schedule is based on the real calendar; it is in the formation of the schedule where most project plans are confronted by reality. A number of projects have had to be radically revised when it was discovered that the planned delivery date actually falls on 25 December.
There are nine inputs to the schedule development process:
Tools and techniques
There are 10 different tools and techniques for developing the project schedule. Most organizations, and indeed project managers, have a preferred method and the PMI does not profess an opinion upon which is better, or how many of them to use. It is entirely project-dependent. We will discuss each of the methods briefly here, as there are many good books devoted entirely to one or more of these tools and techniques.
Schedule network analysis
The application of this technique results in the production of the project schedule. It comprises a number of different tools and techniques itself, such as the critical path method, schedule compression, resource levelling, critical chain method, what-if analysis, and many more. In fact, this technique encompasses the entire process of generating the schedule. Analysis of the schedule network ensures that points of convergence, divergence, conflicts and other inconsistencies are identified and resolved. It also identifies the late and early starts and finishes for the project activities. For large projects this may be achieved by using a software tool, whereas for small projects, schedule network analysis may be seen as a sanity check.
The critical path method
The critical path method was invented by the DuPont Corporation during the 1950s. A critical path is the sequence of project network elements with the longest overall duration. It is used to determine the shortest time to complete the project. The duration of the critical path determines the duration of the entire project. Delaying an element on the critical path directly influences the planned project completion date. For example, in Figure 6.3, the critical path is 10 days (route A B C). The amount of float or waiting time on the project is the time between the tasks not on the critical path finishing and those on the critical path finishing. In Figure 6.3, the float is 1 day. If the duration of task D increases to 8 days then the lower path (route D E) would become the critical path of 11 days.
Figure 6.3. Network diagram showing the critical path
A network diagram showing the duration for activities. Tasks A, B and C take 10 days to complete, tasks D and E take 9 days. The critical path is the longest route through the network diagram; in this example the critical path is A, B and C at 10 days.
This is a technique that shortens the time taken to complete the project without reducing scope. Internal and external factors may cause a project manager to undertake this course of action. For example, a product may need to be launched earlier than planned to maintain competitor advantage. There are two techniques that can be used for schedule compression: crashing and fast tracking. Crashing is when cost and schedule are compared to determine how to obtain the greatest amount of compression for the least incremental cost. Crashing may not always produce a viable alternative and can result in increased cost. Fast tracking is a technique where the project manager runs phases of a project concurrently, when originally they would have been run sequentially. It is important to note that there is always a trade-off when changing elements in the project plan between time, scope, cost or quality; fast tracking a plan often increases the amount of risk associated with it.
What-if scenario planning
When analysing the schedule, it is always useful to ask the question 'what if ...?'. If your project is dependent on the delivery of a specific component by a fixed date, you should consider what would happen if it was delayed. What would the impact on the project be if the component was a day late: would this be any different if it was two months late? Working through this analysis is another sanity check on your schedule. It also provides the basis for contingency planning and in some cases may result in scope changes. There are mathematical models, such as Monte Carlo analysis, that can be used for complicated projects.
Resource levelling is a technique that aligns the schedule to the available resources. For example, your key programme is already committed to a number of projects, so your schedule must be built around them. This may affect the critical path and cost of the project. Another use of resource levelling is to keep spend profiles constant over budgeting periods. This is particularly useful for projects where time is not the greatest constraint. Resource levelling smoothes the peaks and troughs in project resources, making it easier to predict demand over the project life.
Critical chain method
The critical chain method is a schedule network technique that modifies the project schedule to account for limited resources, often by using probabilistic techniques and semi-analytical models to study the network. There are many books and articles that discuss the critical chain method. As a summary, the critical chain method uses network diagrams of the most likely estimate that the tasks will take, determining the critical path. It then builds duration buffers into the critical path at various milestones.
Project management software
There is a wide variety of project management software available, some for managing a project from start to finish and others to achieve a specific task.
Project calendars (discussed in integration management) and resource calendars inform the project manager when tasks are to happen and when resources are available. These calendars should be applied to the schedule as it is developed in order to ensure the finalized schedule is feasible.
Adjusting leads and lags
This technique requires the project manager to revisit the leads and lags applied to the schedule and assess whether they are accurate. It is often the case that later on in the planning the project manager will have a better understanding of the time requirements. This will enable them to revise leads and lags set earlier in the planning cycle.
A schedule model is normally a project management software tool used in conjunction with manual methods of project management, to perform schedule network analysis to generate the project schedule.
There are eight outputs from schedule development. The first output is the project schedule. At its bare minimum the project schedule will contain a start and finish date for each schedule activity. It can include target dates and key milestones and can often be presented graphically, using one or more of the following formats: project schedule network diagrams, bar charts (Gantt charts) and milestone charts. The remaining seven outputs are:
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