Arrow Diagramming Method (ADM)

Every project consists of a number of tasks which must be coordinated and scheduled to meet project goals and deadlines. A project planning network is a graphical representation of the overall project. Its graphical elements indicate activity duration and "precedence relationships," the order in which project tasks must be performed.

Various techniques exist for constructing network diagrams. One popular technique is the arrow diagramming method (ADM). The ADM, also known as the activity-on-arrow (AOA) network, uses arrows to represent activities and nodes to show dependencies.

In the ADM, activities are connected at points called nodes. A node preceding an activity arrow is the start event for that activity. A node following an activity arrow is the end event for that activity.

The ADM uses only finish-to-start (FS) activity dependencies. This means that activity A must finish before activity B can begin.

The first thing to remember when using the ADM is that an activity can't be represented by more than one arrow in the network diagram. Suppose activity A precedes two activities in a network. To avoid duplicating activity A on the diagram, you would need to follow one arrow representing activity A by an end node. Then follow this end node for A by the two successor activities, B and C.

The second thing to remember is that no two activities can have the same begin and end nodes. Instead, if two activities are related or dependent, you can use a "dummy" activity to show the relationship. A dummy uses no resources and is represented by a dashed arrow.

In addition to activities and dependencies, the ADM shows the early and late schedules for the project. Both the early time (TE) and the late time (TL) for an event appear on the event node.

The ADM also allows project managers to specify activity scheduling flexibility by calculating "float." Float is the amount of time available to complete an activity without affecting project duration. To determine a project activity's float, or slack, you would calculate the difference between the activity's late and early schedule times.

Once float has been determined for each event in the network, it is possible to find the critical path through that network. The critical path shows the earliest possible completion time of the entire project. To find the critical path in an AOA network diagram, you would follow the path that connects all events with zero float since activities with a positive float are, of necessity, not on the critical path.

The arrow diagramming method is a method used to construct network diagrams. Arrow diagramming is said to be "event-oriented" because the arrows represent activities. Arrow diagramming reveals the network sequence and timing of activities which is useful in managing the project's schedule.

Precedence Diagramming Method (PDM)

A project is a series of interconnected activities that can be represented by the project network diagram. Various techniques exist for constructing network diagrams. One of the most common is the precedence diagramming method (PDM).

The PDM uses nodes to represent project activities and connecting arrows to show activity dependencies. This technique is also called the activity-on-node (AON) network approach.

To construct a network diagram, you need to consider four types of precedence relationships: finish-to-start (FS), start-to-start (SS), start-to-finish (SF), and finish-to-finish (FF).

• finish-to-start (FS)
  The FS relationship is one in which activity A must finish before activity B can begin. This is the most commonly used type of precedence relationship.
  

• start-to-start (SS)
  The SS relationship is one in which activity A must start before activity B can start. As an example, let activity A be compiling a phone list, and Activity B be calling the people on the list. In this example, compiling the phone list (A) must start before calling the people on the list (B) can start.
  

• start-to-finish (SF)
  The SF relationship is one in which activity A must start before activity B can finish. Let activity A be breathing on one's own. Let activity B be breathing with the aid of a respirator. Breathing on one's own must start (A) before breathing with the aid of a respirator (B) can finish.
  

• finish-to-finish (FF)
  The FF relationship is one in which activity A must finish before activity B can finish. Let activity A be a telemarketing department compiling a phone list. Let activity B be calling the people on the list. Compiling the phone list (A) must finish before calling the people on the list (B) can finish.
  

To convey as much information as clearly as possible, project network diagrams also include early and late schedules.

• the early schedule
  The early schedule is made up of the earliest start (ES) and earliest finish (EF) times. In a project, the ES for an activity is the earliest possible time that the activity can begin. The EF is the earliest possible time that the activity can end.
  
  You can determine the ES for an activity by looking at its predecessors. No predecessors means that the ES is day one, the beginning of the project. One predecessor means that the ES for the activity is dependent on the EF of the predecessor. More than one predecessor means that the ES of the activity depends on the maximum of the EF times of the predecessor activities.
  

• the late schedule
  The late schedule consists of the latest start (LS) and latest finish (LF) times. In a project, the LS and LF are the latest times that an activity can begin and end without causing project delay.
  
  You can calculate the LS and the LF times by using the early schedule. First, set the LF time of the last activity to the EF time of the same activity. Likewise, you can determine the LF time of all immediate predecessor activities by choosing the maximum of the EF times on all predecessor nodes.
  

Once the early and late schedules are in place, you can determine a float for an activity by taking the difference, LF minus EF.

LF - EF = LS - ES

The activity has no float if this number is zero. Float allows for some flexibility in project management and can change as the project progresses.
In a project network diagram, the series of activities that determines the earliest possible completion of the project is called the critical path. The critical path is usually defined as those activities for which float is zero.

To determine the critical path, begin with the first activity in the project. Look at its successors. Compare the successors' float values. Select the one with zero float. This is the second activity on the critical path.

Continue from the second activity on the critical path and compare the float for its successors. Select the activity that has zero float and include it in the critical path.

Continue this process to the final activity for a complete critical path. Ultimately, a project cannot finish any sooner than the time it takes to complete the activities on the critical path.

The PDM represents a project as a network of interrelated activities. The PDM is a way to prepare project activities for scheduling by organizing them in terms of the project's relationships, early and late schedules, float, and critical path. In this way, the PDM allows you to arrive at a realistic, workable project schedule.

Three IT Project Management Tools

Every trade has its tools. As an IT project manager, what do you consider to be your "tools of the trade?"

There are three tools used by IT project managers and team members that are key to the administration of a project. These three tools are project planning software, project estimating software, and presentation tools.

1. Project planning software
Project planning software helps your team define and manage the scope of the project. Many versions of planning software are presently available for project management. You should shop around to determine the best product for the various projects your company undertakes.

Planning software is a valuable tool for creating and managing schedules like Gantt or Pert-type charts and for facilitating communication between all parties involved in the project.

2. Project estimating software
Project estimating software is useful for compiling data, producing charts, managing resources and costs, and performing analyses. Spreadsheets are a common example of estimating software.

3. Presentation tools
Presentation tools help you visually deliver progress reports, produce user manuals, and prepare final reports. The specific needs of your project will help you determine the estimating software and presentation tool you will need.

By determining your project needs ahead of time, you will be able to identify key IT project management tools that will help you and your team effectively complete your next project.