What are activity networks in software engineering[Know More]

Activity Networks in software Engineering
Software Engineering

Activity Networks(Charts)

The foundation of this approach originated from the Special Project Office of the US Navy in 1958. They develop this technique for evaluating the performance of the large development projects.
Here are three stages of activity networks:

  • Identify tasks and estimate duration of times.
  • Arrange in feasible sequence.
  • Draw diagrams.
  • Establish timetable of start and finish times.
  • Establish float.
  • Evaluate and revise as necessary
The activity network of tasks needed to complete a project, showing the order in which the tasks need to be completed and the dependencies between them. This is represented graphically.
The diagram consist of a number of circles, representing events within the development themselves. Each task is individually labelled by it's time duration. Thus the task between events 4 & 5 is planned to take time units. The primary benefits is the identification of the critical path.

Tasks on the critical path therefore needed to be monitored carefully.

Activity Network Types

The degree of difficulty in developing a plan is usually a function of the number of activities or tasks, their sequence, their timing, and the complexity. For small projects, the plan may consist of only a simple flow diagram, bar charts, and computer spreadsheets. For larger projects, there are a number of tools that are used to develop the plans.

Here are two types of Activity Network Diagrams:
  • Program Evaluation and Review Technique 
  • Critical Path Method
Project Evaluation Review Technique (PERT)

Project Evaluation and Review Technique (PERT) is a project management tool that are used to manage, and coordinate tasks within an project. PERT is a methodology developed by the US Navy in the 1950s to manage the Polaris Submarine Missile Program.

Unlike Gantt charts, PERT can be both a cost and a time management system. PERT is organised by events and activities or tasks.
PERT is developed for research and engineered type projects when activity completion times are uncertain. The heart of any PERT chart is a network of tasks needed to be complete a project, showing the order in which the tasks are needed to be completed and the dependencies between them.

PERT charts depicts the tasks,dependencies, duration. Each chart starts with an initiate node from which the first task is originate. If multiple tasks begins with the same time, they are all started from the node or branch from the starting point. Each task is represented by a line, which states it's names,duration,number of peoples assigned to it and in some of the cases the initials of the personnel assigned. The other end of the task line is determined by another node, which identifies the start and another tasks, or the beginning of any slack time i.e. waiting time between tasks.

Steps in Drawing a PERT chart

  • Make a list of the project tasks
  • Mark an identification letter to each task.
  • Determine the duration time for each task.
  • Make a PERT network, number each node,label each task with its task identification letter, connect every node from start to finish, and put each task's duration on the network.
  • Determine the need for any dummy tasks.
  • Determine the early completion time for each task node.
  • Verify the PERT network for correctness.

Benefits of PERT

  • The PERT network is continuously useful to project manager prior to and during a project.
  • PERT is straightforward in its concept and is supported by software.
  • The graphical representation of project's tasks help to show the task interrelationship.
  • It has ability to highlight the project's critical path and task slack time allows the project manager to focus more attention on the critical aspects of the project-time, costs and peoples.
  • It can be use in wide variety of projects.
  • Also PERT is an tool which shows the graphically which tasks must be completed before other than begun.
  • By displaying many task paths, PERT enable the calculation of a critical path. 
  • PERT controls the time and costs during the project and also facilitates finding the right balance between completing a project on time and completing it within the budget.
  • This allows the scheduling and simulation of alternative schedules.
  • PERT forces the manager to plan.
  • It expose all the possible parallelism in the activities and thus helps in allocating resources.

Limitations of PERT

  • In order the PERT network is useful, project tasks have to be clearly defined as well as their relationships to each other.
  • The PERT network doesn't deal  very well with the tasks. It assumes the following tasks begin after their preceding tasks end.
  • It is only good as the time estimates that entered by the project manager.
  • PERT doesn't help in deciding which activities are necessary or how long each will take.

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