and manpower are required. There are four basic types of schedules: progress, material, equipment, and manpower.

Progress schedules coordinate all the projects of a Seabee deployment or all the activities of a single project. They show the sequence, the starting time, the performance time required, and the time required for completion. Material schedules show when the material is needed on the job. They may also show the sequence in which materials should be delivered. Equipment schedules coordinate all the equipment to be used on a project. They also show when it is to be used and the amount of time each piece of equipment is required to perform the work. Labor schedules coordinate the manpower requirements of a project and show the number of personnel required for each activity. In addition, the number of personnel of each rating (Builder, Construction Electrician, Equipment Operator, Steelworker, and Utilitiesman) required for each activity for each period of time may be shown. The time unit shown in a schedule should be some convenient interval, such as a day, a week, or a month.

ELEMENTS

A network represents any sequencing of priorities among the activities that form a project. This sequencing is determined by hard or soft dependencies. Hard dependencies are based upon the physical characteristics of the job, such as the necessity for placing a foundation before building the walls. A hard dependency is normally inflexible. Soft dependencies are based upon practical considerations of policy and may be changed if circumstances demand. The decision to start at the north end of a building, rather than at the south end, is an example.

PRECEDENCE DIAGRAMS

Network procedures are based upon a system that identifies and schedules key events into precedence-related patterns. Since the events are interdependent, proper arrangement helps in monitoring the independent activities and in evaluating project progress. The basic concept is known as the critical path method (CPM). Because the C P M p l a c e s g r e a t e m p h a s i s U p o n t a s k accomplishment, a means of activity identification must be established to track the progress of an activity. The method currently in use is the activity-on-node precedence diagraming method (PDM) where a node is simply the graphic representation of an activity. An example of this is shown in figure 2-24.

Activities

To build a flexible CPM network, the manager needs a reliable means of obtaining project data to be represented by a node. An activity in a precedence diagram is represented by a rectangular box and identified by an activity number.

The left side of the activity block represents the start of the activity. The right side represents the completion. Lines linking the boxes are called connectors. The general direction of flow is evident in the connectors themselves. Figure 2-25 shows a typical activity block used by the NCF.

Activities may be divided into the following two distinct groups:

1. Working Activities - Activities that relate to particular tasks.

2. Critical activities - Activities that together, comprise the longest path through the network. This is represented by two slashes drawn through an activity connector.

The activities are sequenced logically to show the activity flow for the project. The activity flow can be determined by answering the following questions:

Figure 2-24. - Precedence diagram.

Figure 2-25. - Typical activity block.