Purpose
Data flow diagrams show where data comes from, which activities process the data, and if the output results are stored or utilized by another activity or external entity.
Business Analysis Body of Knowledge® (BABOK®)
Data flow diagrams are ideal for depicting the scenarios such as they help the viewers to visualize and understand the data stores, data flows, and business processes. It shows what information is needed within a process, where it is stored, and how it moves to accomplish an objective. As the name implies, the data flow diagram shows the flow of data within the business processes. The data flow diagram is different from a flow chart in that it excludes the cause and effect, sequences and order of the process. Data flow diagrams are user friendly, and easy for designers and end-users to interpret. It represent the work flow or the steps within a business process with a focus on the flow and transformation of business data. Data flow diagrams are the right choice for business process modelling to understand the creation and consumption of data in the individual business processes.
Data flow diagram portray the transformation of data. They are useful for depicting the transformation based system and illustrating the boundaries of a physical, logical, or manual system. It describes the movement and transformation of data between the externals and processes. The output from on external is the input to another process. Data flow diagram consists of multiple layers of abstraction. They are,
- Context Diagram - The highest diagram is the context diagram which represents the entire system. It shows the system in its entirely, as a transformation engine with externals as a source or consumer of data.
- Level 1 Diagram - It illustrate the processes related to the system with respect to input data, output transformed data, and the data stores.
Further process of data flow diagram breaks down the major processes from the level 1 diagram. Logical data flow diagram represent the future state that is what transformations need to occur regardless of the current physical limitations.
Some of the articles related to Data flow diagram techniques are as follows,
The clear and neat data flow diagram depict the good amount of the business requirements graphically. It shows the input, output, and how the input data got converted in to output data. In order to depict the movement and transformation of data, the data flow diagrams use a standardized notations. Some of the elements considered in data flow diagrams are,
- Externals - It is person, system, organization, or any device capable of producing or receiving the data. It is the object which is outside of the system under analysis. Each external must have at-least one data flow going to or coming from in it. They are represented by using a noun inside a rectangle and are found within context level diagrams as well as lower levels of abstraction.
- Data Store - It is a collection of data where data may be read repeatedly and where it can be stored for future use. It is represented as either two parallel lines or as an open-ended rectangle with a label.
- Process - It can be manual or automated activity performed for a business reason. It transforms the data into an output. It is represented as a circle or rectangle with rounded corners.
- Data Flow - The movement of data between the external, a process, and a data store is represented by the data flows. Every data flow will connect to or from a process. It is represented as a line with an arrow displayed between the processes. It is named using a noun.
Advantages of using data flow diagrams are,
- Most users find easy to understand the data flow diagram
- It helps to identify duplicated data elements
- It illustrates connections to other systems
- It can be used as a part of system documentation
- It also helps to identify the boundaries of the system
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