This process involves taking the work packages created in the WBS and breaking them down further (decomposing) in order to reach the activity level; a level small enough to estimate, schedule, monitor and manage. These activities are then sequenced in the next process; activity sequencing.
This is not always done in the real world. Many project managers skip activity definition because they take their WBS down to the activity level rather than the work package level. Other project managers say that they cannot work with a network diagram created at the activity level because it would be too large.
They create the network diagram to the work package level instead of the activity level. Neither of these practices is wrong, just know this for the exam: the PMBOK® Guide states that in activity definition, the WBS is decomposed into activities (schedule activities) and in activity sequencing (described next) those activities are sequenced into the network diagram.
Have you ever felt that the project had too many unknown components to adequately break down the work and schedule it? Be careful, you might really have more than one project! Please see the earlier discussion on this in the Framework lesson.
You might also just have found it better not to plan to the lowest detail in advance, but plan at a higher level and then wait until the project work has begun and the work is more clear to plan the lower levels. This is called rolling wave planning. Summary activities are not planned to the detail needed to manage the work until you start the project management process for that phase of the project life cycle.
Watch out! The existence of rolling wave planning and planning to a higher level than a work package are not excuses for not properly planning a project or making sure all the scope that can be known is known before starting work!
When completed, activity definition will also result in an activity list and the details of the activities (activity attributes) being completed. No part of project management exists alone. Activity definition can lead to a discovery that the WBS or some other part of the project management plan under development needs to be changed. This will result in requested changes to the developing project management plan.
The next process is to take the activities and start to sequence them into how the work will be performed. The result is a network diagram (or project schedule network diagram) which can look like the following picture.
Some people incorrectly call a network diagram a PERT chart. There are extensive exercises to help you draw network diagrams later in this lesson. For the exam, know that, in its pure form, the network diagram shows just dependencies. If activity duration estimates (estimates) are added, the network diagram could also show the critical path.
If plotted out against time (or placed against a calendar-based scale), the network diagram would be a time-scaled schedule network diagram.
Methods to Draw Network Diagrams
There are two ways to draw network diagrams, Precedence Diagramming Method and Arrow Diagramming Method. (GERT is a minor item, but it occasionally shows up on the exam.) Today most network diagrams are created using PDM, described below. You should, however, understand both methods for the exam and MEMORIZE the following attributes of the two methods.
Precedence Diagramming Method (PDM ) or Activity-on-Node (AON) In this method, nodes (or boxes) are used to represent activities, and arrows show activity dependencies.
This type of drawing can have four types of dependencies between activities:
A network diagram drawing method that allows loops between activities. The easiest example is when you have an activity to design a component and then test it. After testing, it may or may not need to be redesigned. GERT is only rarely on the exam and when it does appear, it is most often just a choice on the multiple choice questions.
Types of Dependencies
The sequence of activities is determined based on the following dependencies:
Milestones are significant events within the project schedule. Some examples include: the design is completed, or a deliverable due date from the customer. Milestones can be imposed by the sponsor in the project charter and preliminary project scope statement. What many project managers miss is that additional milestones can be imposed by the project manager during activity sequencing or schedule development, as checkpoints to help control the project.
If the checkpoint in the schedule arrives and all the work planned has been completed, then the project manger has a measure that the project may be progressing as planned. A list of milestones becomes part of the project management plan and is included in the project scope statement and WBS dictionary.
Leads and Lags A lead may be added to start an activity before the predecessor activity is completed. Coding might be able to start five days before the design is finished. A lag is inserted waiting time between activities. For example, you must wait three days after pouring concrete before you can construct the frame for the house.
Requested Changes Watch for changes throughout the planning processes. The creation of a network diagram could easily reveal an additional WBS element. These changes are proposed and addressed as part of integrated change control.
Instead of just asking what is a network diagram, the exam will ask the harder question, “How can the network diagram help you?” Only those who have worked with network diagrams can answer such questions. See how you do with the next exercise.
Describe how the network diagram can help you on the project.
You should know that network diagrams can be used to:
Once the activities are sequenced, the type and quantity of needed resources is determined. Remember that resources include equipment and materials, as well as people. Resources must be planned and coordinated in order to avoid common problems such as lack of resources and resources being taken away from the project.
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