A sequence diagram (also called dependency network, task flow or activity plan) is a tool used in project management. The purpose of this chart is to provide a more complete picture of project work and more accurate time planning and scheduling by depicting activities/assignments and their relationships in the form of a network / targeted graph.
The various types of charts that are widely used can be broadly divided into two categories.
Arrow Activity – In this type of chart, the various activities are depicted by the arrows/edges of the graph, and the vertices represent key dates.
Top Activity – These charts depict each activity as a peak in a graph. Then the arrows depict the dependencies between them.
The Gantt chart is named after the discoverer and Henry Gantt. It is a type of top activity chart and is the most preferred way to look at a project because it visually presents the duration of the individual tasks. The activities in the Gantt chart are arranged horizontally – one line is allocated for each activity, and each vertical line represents a moment in time. This happens as each task is a rectangle whose length is proportional to its duration.
Subsequently, Gantt charts also impose specific indications of activities (brackets) that are constituent, as well as key dates (small diamonds).
A simplified variation of the Gantt chart is commonly known as a timing chart. It has no arrows, but the tabular view of the presentation of tasks over time is preserved. So again each row is reserved for one task and time progresses from left to right. The rows are filled only in those places where the task is active at the specified moment.
These types of charts are popular for their simplicity and for being easily displayed on a table or plain paper.
Critical path method
The Critical Path Method (CPM) is also a very important and widely used technique. In practice, the method of drawing a diagram is not necessarily related to it, but most often the two are combined because important data about the critical path method are shown precisely in this type of diagramming. Typically, activities in this type of chart are drawn as rectangles that describe important details for the particular activity.
Technique for program review and evaluation
The Program Review and Evaluation Technique (PERT) was introduced by technology projects in the US Army in the mid-20th century. Its diagrams are of the type of activity of the arrow and it is specific that each time estimate is made with three values:
- most likely
Statistical values (Triangular distribution or Gamma distribution) are then applied to these values to calculate the expected value. This results in a better estimate of time with a reduced risk of delay.
Like the critical path method, the PERT technique is also embedded in most modern commercial project management software and can be implemented automatically.
Types of activities dependencies
There can be many types of dependencies between different project activities. Point activity charts allow these dependencies to be displayed visually. The various network diagram modeling tools allow one to specify one of the following dependencies.
Finished to get started – this is the most common addiction. Example: To begin assembling an article, the necessary parts must be ready.
Finished to finish. Example: In order for a construction auditor to get the job done, the builders need to get their work done. Only then can he make the final inspection and finish.
Begin to begin. Example: To begin the process of quality control by a customer of a software, the actual work on the product itself must also begin. Otherwise, the client has nothing to control.
It starts to end. Example: In order for contractors at a construction site to believe that they have completed their work, the handover process must begin in order for the client to come and inspect. If the client has remarks, then they have not done their job and have to fix the items that are not in agreement.