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Now that the activity list has been created, the activities must be arranged in a logical sequence. This process calls on the project manager and the project team to identify the logical relationships between activities-and the preferred relationship between activities. This can be accomplished a few different ways:
Computer driven There are many different scheduling and project management software packages available. These programs can help the project manager and the project team determine which actions need to happen in what order-and with what level of discretion.
Manual process In smaller projects, and on larger projects in the early phases, manual sequencing may be preferred. An advantage of manual sequencing is that it's easier to move around dependencies and activities than in some programs.
A combination of manual and computer-driven scheduling
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'Sticky notes' can help sequence events. Put your activities on sticky notes and then plot them out on a white board. Draw arrows to show the relationship between activities. Want to make a change? It's easy to rearrange the notes and the relationships.
Figure 6-3 shows the complete process of activity sequencing. There are many approaches to completing the activity sequencing. Perhaps the greatest approach, however, is that activity sequencing is done with the project team, not as a solo activity.
Figure 6-3: Activity sequencing relies on inputs to create the final sequence of events.
The project manager must rely on the project team and the inputs to activity sequencing:
Activity list The activity list we've just discussed-it's the list of actions needed to complete the project deliverables.
Product description The product description is needed since it may influence the sequence of events. For example, in construction, technology, or community planning (among other project types), the product description may include requirements that will logically affect the planning of activity sequencing.
Mandatory dependencies These dependencies are the natural order of activities. For example, you cannot begin building your house until your foundation is in place. These relationships are called hard logic.
Discretionary dependencies These dependencies are the preferred order of activities. Project managers should use these relationships at their 'discretion' and document the logic behind the decision. Discretionary dependencies allow activities to happen in a preferred order because of best practices, conditions unique to the project work, or external events. For example, a painting project typically allows the primer and the paint to be applied within hours of each other. Due to the expected high humidity during the project, however, all of the building will be completely primed before the paint can be applied. These relationships are also known as soft logic, preferred logic, or preferential logic.
Milestones must be
Network diagrams visualize the project work. A network diagram shows the relationship of the work activities and how the work will progress from start to completion. Network diagrams can be extremely complex or easy to create and configure. Most network diagrams in today's project management environment use an approach called 'activity-on-node' to
The Precedence Diagramming Method (PDM) is the most common method of arranging the project work visually. The PDM puts the activities in boxes, called nodes, and connects the boxes with arrows. The arrows represent the relationship and the dependencies of the work packages. The following illustration shows a simple network diagram using PDM.
PDM is also known as AON- activity-on-node. It's the most common approach to network diagramming since it's used by most project management information systems but can also be done manually.
Relationships between activities in a PDM
Figure 6-4: PDM relationships can vary, but most use the
Finish-to-start (FS) This relationship means Task A must complete before Task B can begin. This is the most common relationship. Example: The foundation must be set before the framing can begin.
This relationship means Task A must start before Task B can start. This relationship allows both activities to happen in tandem. For example, a crew of
This relationship means Task A must complete before Task B does. Ideally, two
This relationship is unusual and is rarely used. It requires that Task A start so that Task B may finish. Such relationships may be
The Arrow Diagramming Method (ADM) approach to activity sequencing uses arrows to represent the activities. The arrows are 'connected' on nodes. ADM only uses finish-to-start relationships. In some instances, dummy activities are required to express the logical relationship between two activities. A
Only professional scheduling
ADM is an example of activity-on-arrow (AOA) networks. This approach is not as popular as PDM, but may still be
Conditional diagramming methods are more complex and structured than ADM or PDM. Conditional diagramming methods include system dynamics and the graphical evaluation and review technique (GERT). These models allow for
Just as a project manager can rely on WBS templates, there may be network templates available to streamline the planning process or to conform to a predetermined standard. Network templates can represent an entire project if appropriate, though portions of a network template, such as the required project management activities, are common.
Note that GERT allows for conditional advancement. ADM and PDM offer no loops or branching.
The portions of a network template are also known as subnets or fragnets. Subnets are often associated with repetitive actions within a network diagram. For example, each floor in a high-rise apartment building may undergo the same or similar actions during construction. Rather than complete the network diagram for each floor, a subnet can be implemented.
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