Network Diagram

Quick reference

• 00:05 Hi I'm Ray Sheen, I'd like to talk with you about one of my favorite project
• 00:08 scheduling techniques, the Network Diagram.
• 00:11 The Network Diagram, is a flow chart of the project activities.
• 00:17 It shows the schedule relationship between tasks.
• 00:20 We can see how tasks are connected and how they impact each other.
• 00:24 The Project Management Body of Knowledge, the PMBOK Guide,
• 00:27 defines a Project Schedule Network Diagram as a graphic representation
• 00:32 of the logical relationships among project schedule activities.
• 00:35 Each task is represented by a node.
• 00:38 They are connected by arrows showing the relationships between the tasks.
• 00:42 We can see for each tasks, what other tasks are predecessors, and
• 00:46 what are successors?
• 00:48 This creates a focus on the handoffs between tasks, the completion of one and
• 00:53 the start of the next.
• 00:54 We can follow the progress to be sure that the ball is not dropped.
• 00:58 There are several important uses of the Network Diagram.
• 01:01 First of all, our advanced schedule analytical techniques require a network
• 01:04 diagram, and I'll talk more about those techniques in another lesson.
• 01:09 Second, I find this to be the best tool for
• 01:12 tracking projects with high uncertainty in the project estimates.
• 01:16 We know what to do, but we don't know how long it will take.
• 01:18 Other project scheduling techniques like the Gantt Chart
• 01:21 require a precise duration estimate.
• 01:24 With the Network Diagram, I encourage everyone to complete their task
• 01:27 as fast as possible, and then hand things off to the next task.
• 01:31 The key to network diagrams are the arrows connecting the tasks called dependencies.
• 01:37 These dependencies show which tasks must be completed before the next
• 01:40 task can start.
• 01:42 There are three types of dependencies.
• 01:44 The mandatory dependency is a dependency that cannot be broken.
• 01:48 It is usually based upon some physical relationship between the tasks.
• 01:53 For instance, if I have a testing task,
• 01:55 I must first create the test samples before I can conduct the test.
• 01:59 Without test samples, it's impossible to conduct a test.
• 02:04 The next type of dependency is a discretionary dependency.
• 02:07 Now these can't be broken, but only by adding risk to the project.
• 02:11 In fact, many times the dependency was created in order to reduce risk.
• 02:16 Back to our test example.
• 02:18 We created dependency that says, the testers cannot do the setup to prepare for
• 02:22 the test, until the test plan is approved.
• 02:25 This reduces the risk that the test setup is wrong and must be redone.
• 02:29 However, if we consider the likelihood of not getting approval for the test plan
• 02:33 is low, and we need to accelerate the project because of delays in other tasks,
• 02:37 we can break that dependency and do the set up before the test plan is approved.
• 02:42 We won't start testing without the approval, that might be too risky.
• 02:45 But we can do the set up.
• 02:47 The third dependency is an external dependency.
• 02:50 Although, these dependencies are outside the control of the project leader,
• 02:53 they can be broken in exceptional cases by stakeholders.
• 02:57 Continue with our example.
• 02:58 We may have test samples in an approved test plan, but
• 03:01 a higher priority project is using the test facility.
• 03:04 And we're delayed for several weeks until they finish.
• 03:07 However, senior managers can step in and change the priorities to allow
• 03:12 us access to the test facility even though the other project isn't finished.
• 03:16 Understanding the nature of the dependency will enable the project team
• 03:20 to manage them.
• 03:22 Now, creating a network diagram is pretty easy.
• 03:25 First, we identify the dependencies for each task by asking
• 03:29 what does that task require to be done before it can be started?
• 03:33 Next, we arrange the tasks in their normal sequence based upon the dependencies just
• 03:37 identified.
• 03:38 Now, plot each of the dependencies between those tasks so
• 03:41 we can see the relationships.
• 03:43 Finally, look for loops and danglers.
• 03:46 Loops exist when there are several task that may repeat over and over again.
• 03:50 The problem with these project is knowing how the estimate the number of iterations
• 03:55 through the loop.
• 03:56 Do they repeat twice?
• 03:57 Three times?
• 03:58 Four times?
• 04:00 Place a counter on the loop and create a maximum number before it must stop and
• 04:04 be replanned by the core team.
• 04:06 Loops should also be tracked as project risks.
• 04:09 Danglers are tasks that either have no starting relationship or
• 04:12 finishing relationship.
• 04:14 The lack of relationship makes it unclear what the task is related to.
• 04:17 If there's no predecessor relationship,
• 04:20 the project team doesn't know when to initiate the task.
• 04:23 If there is no successor relationship, we must ask the question,
• 04:26 why are we even doing this work since no one needs it?
• 04:30 There are a few hints and tips associated with network diagrams.
• 04:33 First, use this technique to track the handoffs between tasks.
• 04:37 It's a great way of enabling team members to work together
• 04:40 to move the project forward.
• 04:42 I often use a network diagram for managing small projects with high uncertainty,
• 04:46 because it's so easy to understand and follow.
• 04:49 However, it does add extra work for the project manager who must translate that
• 04:53 network into a calendar-based milestone chart for communication with stakeholders.
• 04:57 Even on large projects, I have often created a summary level,
• 05:00 milestone or Gantt chart for reporting purposes.
• 05:02 But use the network diagram for each major deliverable or phase.
• 05:07 Finally, in times of crisis, it's often the best technique to use.
• 05:11 During crisis, it may be impossible to create precise estimates, but
• 05:15 the flow of activities can be set.
• 05:17 Use the Network Diagram to communicate your plan with both the team and
• 05:20 the stakeholders.
• 05:21 And then, if you get more resources to resolve the crisis,
• 05:25 you'll know how to put them to best use.
• 05:27 As I've said, I like to use the Network Diagram.
• 05:31 It's a great way to illustrate and
• 05:33 manage the flow of activities through the lifecycle of a project.

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