Arrow Diagram Also called: PERT program evaluation and review technique chart The arrow diagram shows the required order of tasks in a project or process, the best schedule for the entire project, and potential scheduling and resource problems and their solutions. This is the flow of critical steps where delays will affect the timing of the entire project and where addition of resources can speed up the project.
The data flow diagram is a hierarchy of diagram consist of: It contains a process shape that represents the system to model, in this case, the "CS System". It also shows the participants who will interact with the system, called the external entities.
In this example, CS Assistant and Passenger are the two entities who will interact with the system. In between the process and the external entities, there are data flow connectors that indicate the existence of information exchange between the entities and the system.
Context DFD is the entrance of a data flow model.
It contains one and only one process and does not show any data store. Read through the diagram and then we will introduce some of the key concepts based on this diagram.
Although there is no design guidelines that governs the positioning of shapes in a Data Flow Diagram, we tend to put the processes in the middle and data stores and external entities on the sides to make it easier to comprehend.
Based on the diagram, we know that a Passenger can receive Transport details from the Inquiry Transport Details process, and the details are provided by the data stores Transport Details and Railway Live Statistic.
While data stored in Transport Details are persistent data indicated by the label "D"data stored in Railway Live Statistic are transient data that are held for a short time indicated by the label "T".
A callout shape is used to list out the kind of details that can be inquired by passenger. CS Assistant can initiate the Buy Souvenir process, which will result in having the Order details stored in the Order data store. Although customer is the real person who buy souvenir, it is the CS Assistant who accesses the system for storing the order details.
CS Assistant can also initiate the Buy Ticket process by providing Order details and the details will be stored again in the Order data store. Data Flow Diagram is a high level diagram that is drawn with a high degree of abstraction.
The data store Order which is drawn here does not necessarily imply a real order database or order table in a database. The way how order details are stored physically is to be decided later on when implementing the system.
Finally, CS Assistant can initiate the Report Lost process by providing the Incident and item details and the information will be stored in the Lost Item database.
The letter indicates the kind of data the data store holds. Besides computerized data, data can also be held for a short time in temporary.
Sometimes, data is stored without the use of a computer. Finally, if the data is stored without using computer and also is held for a short time, this is known as manual transient data and is represented by T M.
Be aware of the level of details In this Data Flow Diagram example, the word "details" is used many times when labeling data.
We have "transport details" and "order details". What if we write them explicitly as "route information, train times and delays", "souvenir name, quantity and amount" and "ticket type and amount"?
Well, there is no definite answer to this question but try to ask yourself a question when making a decision.ashio-midori.com is free online diagram software for making flowcharts, process diagrams, org charts, UML, ER and network diagrams.
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A flowchart is a diagram that illustrates how a process works. Instead of using words to describe the interactions between people, software, or other ‘actors’ in an activity, the flowchart shows this via shapes, symbols, and directional lines.
The term "Process Map" or process flow chart is used to describe a process. Do you know the different types of process maps?
Process Flowchart (Process Flow Mapping) Process flowchart or PFD is also known as the system flow diagram or SFD. The main reason of using process flowchart is to show the relation between major parts of the system.
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