Adding the Logic Links Using Primavera P6 Software in Melbourne
The logic is added to the schedule to provide the order in which the activities must be undertaken.
The logic is designated by indicating the predecessors to, or the successors from, each activity. There are two methods that Primavera software uses to sequence activities:
- Precedence Diagramming Method (PDM), and
- Arrow Diagramming (ADM).
Most current project planning and scheduling software, including Primavera, uses PDM. You can create a PDM diagram using the Network Diagram function.
There are several types of dependencies that may be used:
1. Mandatory dependencies, also known as Hard Logic or Primary Logic, are relationships between activities that may not be broken. For example, a hole has to be dug before it is filled with concrete, or a computer delivered before software is loaded.
2. Discretionary dependencies, also known as Sequencing Logic or Soft Logic or Secondary Logic, are relationships between activities that may be changed when the plan is changed. For example, if there are five holes to be excavated and only one machine available, or five computers to be assembled and one person available to work on them, then the order of these activities could be set with sequencing logic yet changed at a later date.
Both Mandatory dependencies and Discretionary dependencies are entered into Primavera P6 as activity relationships or logic links. The software does not provide a method of identifying the type of relationship because notes or codes may not be attached to relationships. A Note may be added to either the predecessor or the successor activity to explain the relationship.
- External dependencies are usually events outside the control of the project team that impact the schedule. An example would be the availability of a site to start work. This is usually represented in Primavera by a Milestone that has a constraint applied to it. This topic is discussed in more detail in the next section.
The P6 software will calculate the start and finish dates for each activity. The end date of the project is calculated from the start date of the project, the logic amongst the activities, any Leads(often referred to as Negative Lag)or Lags applied to the logic and durations of the activities.